Trigonometric Functions and Reference Angles

To evaluate trigonometric functions using reference angles

To learn how to use a calculator for trigonometric functions

To understand the history of trigonometry

To memorize the unit circle

An angle that is always negative

An angle that is always positive

An angle that is a multiple of 90 degrees

An angle that shares the same terminal side as another angle

First quadrant

Second quadrant

Fourth quadrant

Third quadrant

An angle that is always 180 degrees

An acute angle formed with the x-axis

An angle that is always 360 degrees

An angle that is always 90 degrees

Add the angle to 360 degrees

Add the angle to 180 degrees

Subtract the angle from 180 degrees

Subtract the angle from 360 degrees

120 degrees

100 degrees

80 degrees

60 degrees

By using a calculator

By using the Pythagorean theorem

By using a simple trig chart

By guessing

Zero

Negative one

Radical three over two

1/2

To ensure the reference angle is correct

To memorize the unit circle

To make the drawing look better

To avoid using a calculator

It doesn't affect the result

It makes the calculation faster

It gives the wrong reference angle

It makes the angle negative