### Zeros of sine-type functions

The Graph of the Sine Function. Our goal right now is to graph the function. When we graph functions, we often say to graph the function on an interval. We use interval notation to describe the interval. Interval notation has the form , which means the interval begins at a and ends at b. Graph the sine function on the interval.

Plot all the points from the last column of the table above. Connect the points with a smooth curve. The values increase from 0 to 1 and then decrease from 1 to 0. Note that our input is , the measure of the angle in radians, and that the horizontal axis is labeled , not x. You could simply plot all the points from the last column and continue the graph in the last example. But notice the following: the values in the third column or y -coordinates of the points have the opposite values of the points that we just graphed.

This means that instead of plotting points above the -axis, you will be plotting points below the -axis. Also, the inputs and outputs are spaced out in the same fashion for this part of the graph as they were for the first part of the graph. Imagine you are on 1, 0 and you walk around the circle one complete time and then you walk a little more to end up at x , y. All of the trigonometric functions for these two angles are computed using the coordinates of this point. This means that , , , and the same is true for the three reciprocal functions. In other words, as we go around the same circle a second time, at the same locations on the circle we will get the same values for the y -coordinate and the x -coordinate that we did the first time around the circle.

## Sine: 3D plots over the complex plane

The same reasoning that we used above works for negative angles. Because they are coterminal angles , they intersect the unit circle at the same point and therefore have the same coordinates. Therefore, , , and so on for the other trigonometric functions. Notice that we could rewrite the first equation as. Sketch the graph of the sine function on the interval. Since the equation is true for any angle, it is an identity. We can use this identity to continue the graph of the sine function in either direction.

For example:. What is the value of? Perhaps you simplified incorrectly and thought this was equal to. The correct answer is. You may have incorrectly converted from degrees to radians or confused sine and cosine. Remember that. You may have simplified incorrectly and thought this was equal to. The Graph of the Cosine Function. Now our goal is to graph. We will go through the same procedure as we did for the sine function, and the result will be similar.

Graph the cosine function on the interval. Connect them with a smooth curve. The values decrease from 1 to 0 and also continue to decrease from 0 to. Once again, our input is , the measure of the angle in radians, and the horizontal axis is labeled , not x.

Again, you could simply plot all the points from the last column and continue the graph. Instead, compare the values in the third columns of the two tables: they are the same numbers, but in the reverse order. These are the y -coordinates of the points. Here it is:. The next step is to continue the graph for input values. When we were in the process of graphing the sine function, we established the following identity:. This equation tells us that when we go around the circle a second time, we are going to get the same values for as we did for. In other words, as we go around the same circle a second time, at the same locations on the circle we will get the same values for the x -coordinate that we did the first time around the circle.

Sketch the graph of the cosine function on the interval. You can use this to continue to extend the graph in both directions. Another way to describe this is to say that if you substitute a number and its opposite into the function, you will get the same value as the previous equation. For example, , , or in general,. We say that the graph is symmetric about the y-axis.

The diagram below shows two points taken from a symmetric graph. The height of the points at opposite inputs is the same. The height is the value of the function. A function whose graph is symmetric about the y -axis has. What is the range of the cosine function? A all values in the interval. B all values in the interval. C all values in the interval. You were probably looking at the y -values, which is the correct thing to do. However, you chose only part of the range. The range is the set of all y -values that the function can have; in this case that would be.

The correct answer is B. The graph of the function extends forever in both directions, so its domain is all real numbers. Both graphs have the same shape, but with different ranges of values, and different periods. Sine squared has only positive values, but twice the number of periods. The sine squared function can be expressed as a modified sine wave from the Pythagorean identity and power reduction by the cosine double-angle formula: . The table below displays many of the key properties of the sine function sign, monotonicity, convexity , arranged by the quadrant of the argument.

Using only geometry and properties of limits , it can be shown that the derivative of sine is cosine, and that the derivative of cosine is the negative of sine. The series formulas for the sine and cosine are uniquely determined, up to the choice of unit for angles, by the requirements that. The radian is the unit that leads to the expansion with leading coefficient 1 for the sine and is determined by the additional requirement that. The coefficients for both the sine and cosine series may therefore be derived by substituting their expansions into the pythagorean and double angle identities, taking the leading coefficient for the sine to be 1, and matching the remaining coefficients.

In general, mathematically important relationships between the sine and cosine functions and the exponential function see, for example, Euler's formula are substantially simplified when angles are expressed in radians, rather than in degrees, grads or other units. Therefore, in most branches of mathematics beyond practical geometry, angles are generally assumed to be expressed in radians. A similar series is Gregory's series for arctan , which is obtained by omitting the factorials in the denominator.

The sine function can also be represented as a generalized continued fraction :. The continued fraction representation can be derived from Euler's continued fraction formula and expresses the real number values, both rational and irrational , of the sine function. This integral is an elliptic integral of the second kind. The Fourier series for this correction can be written in closed form using special functions, but it is perhaps more instructive to write the decimal approximations of the Fourier coefficients.

The sine curve arc length from 0 to x is. The law of sines states that for an arbitrary triangle with sides a , b , and c and angles opposite those sides A , B and C :. It can be proven by dividing the triangle into two right ones and using the above definition of sine. The law of sines is useful for computing the lengths of the unknown sides in a triangle if two angles and one side are known.

This is a common situation occurring in triangulation , a technique to determine unknown distances by measuring two angles and an accessible enclosed distance. For certain integral numbers x of degrees, the value of sin x is particularly simple. A table of some of these values is given below.

Although dealing with complex numbers, sine's parameter in this usage is still a real number.

## How to Find Zeros of a Function

Sine can also take a complex number as an argument. This is an entire function.

• Yearbook of International Humanitarian Law Volume 15, 2012.
• Principles and Practice of Psychopharmacotherapy (4th Edition).
• Brain Tumors.
• Graph of Cos Function.

Also, for purely real x ,. It is also sometimes useful to express the complex sine function in terms of the real and imaginary parts of its argument:. Using the partial fraction expansion technique in complex analysis , one can find that the infinite series. Similarly, one can show that. Alternatively, the infinite product for the sine can be proved using complex Fourier series. It follows that. As a holomorphic function , sin z is a 2D solution of Laplace's equation :.

The complex sine function is also related to the level curves of pendulums. While the early study of trigonometry can be traced to antiquity, the trigonometric functions as they are in use today were developed in the medieval period. The first published use of the abbreviations 'sin', 'cos', and 'tan' is by the 16th century French mathematician Albert Girard ; these were further promulgated by Euler see below. The Opus palatinum de triangulis of Georg Joachim Rheticus , a student of Copernicus , was probably the first in Europe to define trigonometric functions directly in terms of right triangles instead of circles, with tables for all six trigonometric functions; this work was finished by Rheticus' student Valentin Otho in In a paper published in , Leibniz proved that sin x is not an algebraic function of x.

When the Arabic texts were translated in the 12th century into Latin by Gerard of Cremona , he used the Latin equivalent for "bosom", sinus which means "bosom" or "bay" or "fold".

### Tell us what we can do better:

The sine function, along with other trigonometric functions, is widely available across programming languages and platforms. In computing, it is typically abbreviated to sin.

• MATH USSR IZV, , 14 (1), 79–?
• Graph of Sin Function;

In programming languages, sin is typically either a built-in function or found within the language's standard math library. For example, the C standard library defines sine functions within math. The parameter of each is a floating point value, specifying the angle in radians. Each function returns the same data type as it accepts. Many other trigonometric functions are also defined in math. Similarly, Python defines math. Complex sine functions are also available within the cmath module, e.

### Roots of Polynomials

CPython 's math functions call the C math library, and use a double-precision floating-point format. There is no standard algorithm for calculating sine. IEEE , the most widely used standard for floating-point computation, does not address calculating trigonometric functions such as sine. This can lead to different results for different algorithms, especially for special circumstances such as very large inputs, e. A once common programming optimization, used especially in 3D graphics, was to pre-calculate a table of sine values, for example one value per degree.

• My Own Private Germany: Daniel Paul Schrebers Secret History of Modernity!
• Programming the Microsoft Windows Driver Model!
• 10 Secret Trig Functions Your Math Teachers Never Taught You - Scientific American Blog Network.
• The Bonegatherer.
• If on a Winters Night a Traveler!
• Select a Web Site;

This allowed results to be looked up from a table rather than being calculated in real time. With modern CPU architectures this method may offer no advantage.