Question

heya!!!

Express cos 2A in terms of cos 4A..

Answer 1

Answer:

√(1 + cos 4A)/2

Step-by-step explanation:

Theorem:

cos² 2A = (2 cos² 2A)/2

             = (1 - 1 + 2cos²2A)/2

             = [(1 + (2 cos²(2A) - 1)/2]

∴ cos 2A = 2 cos² A - 1

             = [1 + cos2(2A)/2]

             = [1 + cos4A/2]

Now,

We know that cos²(2A) = [1 + cos4A]/2

cos 2A = √(1 + cos 4A)/2

Hope it helps!

Answer 2

hey mate hope this helps you