Question

Please help me. I'll mark as Brainliest and 50 points

Answer 1

Hey mate!

Here's your answer!!

✮Kindly refer to the given attachment✮

$hope \: it \: helps \: you...$
✌ ✌ ✌

#BE BRAINLY

Answer 2

Let's solve in different points by considering smaller units

Cos2a + Cos2b = 2Cos(a+b)Cos(a-b)

                            =2Cos(270-c)Cos(a-b)

                           =  -2Sin(c)Cos(a-b)

 

Cos2c = 1- 2Sin22c

 

4SinaSinbSinc = 2(2SinaSinb)Sinc

                          = 2[Cos(a-b) - Cos(a+b)]Sinc

                          = 2[Cos(a-b) - Cos(270-c)]Sinc

                          = 2[cos(a-b) + Sinc]Sinc

                          = 2Cos(a-b)Sinc + 2Sin2c 

now add the results of these three parts and get the desired 

ANS = 1