Find the value of arccos-12
Find the value of cos-1-12
Let cos-1-12=P
⇒cosP=-12
The period of the cosine function is from 0 to π
Hence, the principal solution lies between 0 to π
⇒cosP=cos2π3
⇒P=2π3
Hence the value of cos-1-12 is 2π3