Question

cos 5pi ÷3
HOW TO SOLVE BY FORMULA

Answer 1

5pi÷3=150
we can also write it as 90*2-30
we have formula cos(90*n+or-★)
★ as thita
if n is odd digit then cos(90*n+or-★)=sin★
we have to check sin is in which quadrant and take value +ve or -ve
if n is even the value is cos★ just like sine
here n is even and★ is in II quadrant
hence cos( 90*2-30 )=-cos30=-√3/2

hope i have helped you