Trigonometry Examples

Find the Exact Value cos(-(5pi)/4)
Step 1
Add full rotations of until the angle is greater than or equal to and less than .
Step 2
Apply the reference angle by finding the angle with equivalent trig values in the first quadrant. Make the expression negative because cosine is negative in the second quadrant.
Step 3
The exact value of is .
Step 4
The result can be shown in multiple forms.
Exact Form:
Decimal Form: