Question

it cos(A) - 1/2 Then value
of cos (3A) =​

Answer 1

Step-by-step explanation:

cos3a=1/2

cos3a=cos(pi/3)

If cosx=cosy

X=2×n×pi +-(pi/3)

when n=0

x=(pi/3) or (-pi/3)->rejected as a lies btw 0 to 2 pi

when n=1

x=(5pi/3) or (-7pi/3)->rejected

For n>2 values are greater than 2pi

so x can be pi/3 or 5pi/3

for x=pi/3

sinx=sqrt(3)/2

for x=5pi/3

sinx=-sqrt(3)/2

So sinx can take two values sqrt(3)/2 and -sqrt(3)/2.