Quick Review 4-3

Unit 4 - Objective 3 - Values of Trigonometric Functions

Signs of trigonometric functions in all four Quadrants.

Reference Angles are always next to the x-axis

Given the reference angle , you can find the angle in the appropriate quadrant and given angle , you can find its reference angle.

1st Quadrant	2nd Quadrant
3rd Quadrant	4th Quadrant

The unit circle can be used to find trigonometric function for angles dividing the quadrants.

On the unit circle	x^2 + y^2 = 1 and	x = cos
		y = sin

Examples:

sin 90° = y = 1
cos 90° = x = 0
tan 90° = y/x = 1/0 = undefined

cot 90° = 1/tan 90° = x/y = 0/1 = 0
sec 90° = 1/cos 90° = 1/0 = undefined
csc 90° = 1/sin 90° = 1/1 = 1

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Special Triangles

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Examples:

1.	Find the value for cos 150°	150° is in the 2nd quadrant, cos is negative in the 2nd quadrant, and the reference angle is 180° - 150° = 30° So cos 150° =

2.	Find for tan = if 0° < or = < 360°	The reference angle for tan = is 30° and tan is positive in the 1st and 3rd quadrants so: is 30°, 180° + 30° = 210°