Precalculus Examples

$810$

Step 1

Find an angle that is positive, less than $360 °$ , and coterminal with $810 °$ .

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Step 1.1

Subtract $360 °$ from $810 °$ .

$810 ° - 360 °$

Step 1.2

The resulting angle of $450 °$ is positive and coterminal with $810 °$ but isn't less than $360 °$ . Repeat the step.

$450 °$

Step 1.3

Subtract $360 °$ from $450 °$ .

$450 ° - 360 °$

Step 1.4

The resulting angle of $90 °$ is positive, less than $360 °$ , and coterminal with $810 °$ .

$90 °$

Step 2

Since $90 °$ is in the first quadrant, the reference angle is $90 °$ .

$90 °$