How do you find the exact value of cos1(22)?

1 Answer
Jun 28, 2015

cos1(22)=135oor225o
XXXXif we restrict the range to [0,360o)

Explanation:

(22)=(12)

If cos(12)=θ then cos(θ)=(12)

If θε[0,2π)
we have the two possibilities indicated in the diagram below:
enter image source here
with θ (measuring from the positive x-axis) as either
180o45o=135o
or
180o+45o=225o

For people who prefer their angles in radians that is
ππ4=3π4
or
π+π4=5π4