Question

help me out pls frnds​

Answer 1

Hey there!

Answer:

√3 / √2   (without rationalizing)

√6/2   (after rationalizing)

Step-by-step explanation:

Given,

cos 75° + cos 15°

We know,

cos x + cos y = 2 cos(x+y)/2 * cos(x-y) / 2

cos(75 + 15)   = 2 cos(75+15)/2 * cos(75-15)/2

                       = 2cos(90/2) * cos(60/2)

                       = 2cos(45)*cos(30)

                       = 2*(1/√2)*(√3/2)

                       = √3 / √2

On rationalizing,                      

                      = (√6)/2

Hope It Helps You!