# §1.6 Trigonometric Review

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§1.6 Trigonometric Review
The student will learn about: angles in degree and radian measure, trigonometric functions, graphs of sine and cosine functions, and the four other trigonometric functions.

§1.6 Trigonometric Review
What follows is basic information about the trigonometric essentials you will need for calculus. It is not complete and assumes you have a full knowledge of trigonometric functions.

Degrees and Radians Angles are measured in degrees where there are 360º in a circle. Angles are also measured in radians where there are 2π radians in a circle. Degree-Radian Conversion Formula Example 1. Convert 90º to radians.

Example 2. Convert π/3 radians to degrees. = 60 º Some Important Angles Radian π/6 π/4 π/3 π/2 π Degree 30º 45º 60º 90º 180º 360º

Trigonometric Functions
Consider a unit circle with center at the origin. Let point P be on the circle and form an angle of θ (in radians) with the positive x axis. θ (1, 0) (0, 1) P (x, y) The cosine θ is the abscissa of point p, i.e. x = cosine θ. The sine θ is the ordinate of point p, i.e. y = sine θ. To find the value of either the sine or cosine functions use the sin and cos keys of your calculator. Make sure you are in the correct mode, [either degrees or radians] pertaining to the problem.

Trigonometric Functions
Consider a unit circle with center at the origin. Let point P be on the circle and form an angle of θ (in radians) with the positive x axis. θ (1, 0) (0, 1) P (x, y) The cosine θ is the abscissa of point p, i.e. x = cosine θ. The sine θ is the ordinate of point p, i.e. y = sine θ. Remember the sign “+/-” of the abscissa and the ordinate in the different quadrants. That will help you get their signs correct in the future.

Trigonometric Functions
The cosine θ is the abscissa of point p, i.e. x = cosine θ. The sine θ is the ordinate of point p, i.e. y = sine θ. The sine and cosine of some special angles Radian π/6 π/4 π/3 π/2 π Degree 30º 45º 60º 90º 180º 360º Sine 1/2 2/2 3/2 1 Cosine - 1 The values in aqua will repeat. Know them!

Graphs of Sine and Cosine
f (x) = sine x is a periodic function that repeats every 2π radians and can be found on your graphing calculator as: f (x) = cosine x is a periodic function that repeats every 2π radians and can be found on your graphing calculator as:

Graphs of Sine and Cosine
y = sin x y = cos x Being able to picture these graphs in my mind has helped me a lot in determining the numeric value of a trig function. If you combine this information with the basic numerical information given earlier you will be in pretty good shape for getting the correct numerical values for the trig functions.

Four Other Trig Functions
Four Other Trigonometric Functions These functions may also be graphed on your calculator.

Four Other Trig Functions
Four Other Trigonometric Functions These functions may also be graphed on your calculator.

Trigonometric Identities
There are literally hundreds of trig identities. Several of the most useful follow. Reciprocal identities

Trigonometric Identities
Pythagorean Identities sin 2 x + cos 2 x = 1 1 + tan 2 x = sec 2 x 1 + cot 2 x = csc 2 x Quotient Identities

Trigonometric Identities
Sum Angle Identities

Trigonometric Identities
Double Angle Identities

Trigonometric Identities
And lots more Handout

Summary. We defined the six trigonometric functions.
Degree-Radian Conversion Formula We defined the six trigonometric functions. We examined the graphs of the trigonometric functions. We examined some trig identities. We are now ready to continue our study of calculus using the trigonometric functions.

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