suppose cosA is given if only one value of cos(A/2 ) is possible then A is must be

Options

A. An odd multiple of `90^(@)`
B. A multiple of `90^(@)`
C. An odd multiple of `180^(@)`
D. A multiple of `180^(@)`

Answer

C

Explanation

Given , `"cos"(A)/(2)`has only one value.
We know , `cosA=2" cos"^(2)(A)/(2)-1`
`rArr2" cos"^(2)(A)/(2)=cosA+1rArr"cos"(A)/(2)=sqrt((cosA+1)/(2))`
Since , `"cos"(A)/(2)` is single value , `(cosA+1)/(2)=0`
`rArrcosA=-1`
So , A isn an odd multiple of `180^(@)`.