Question

Plz guys solve this (3rd question)

Answer 1

Answer:

LHS

cosx+{-cosx}-{-cosx}+{-cosx}

2cosx-2cosx

0=RHS

Answer 2

Answer:

$\cos x+ \sin(270^{o} -x)+\sin (270^{o}+x)+\cos (180^{o}+x)$

if you know the rule after school to college or add sugar to coffee  then apply that you will get

$\cos x+(-\cos x)+(-\cos x)+(-\cos x)\\\cos x-\cos x-\cos x-\cos x\\=-2\cos x$

Step-by-step explanation: