Question

Prove that: cos520 + cos680 + cos1720 = 0.​

Answer 1

let cos520 be 0

let cos680 be 0

let cos1720 be 0

SO,0+0+0=0

HENCE PROVED

Answer 2

let cos 520 be 0

let cos 680 be 0

let cos 1720 be 0

So, 0+0+0=0