Question

Question #f198d

Answer 1

`cos330^@=cos(270^@+60^@)` is OK, but,

`cos(270^@+60^@)=cos60^@` is NOT CORRECT.

In fact, `cos(270^@+theta)=sintheta,` and, in this accordance,

`cos(270^@+60^@)=sin60^@=sqrt3/2.`

Explanation: