Answer:
The answer w'll be obtained using formulas
cos(a+b) = cosacosb - sinasinb
cos(a-b) = cosacosb + sinasinb
Explanation:
Using the trigonometric formula of addition and subtraction of cosine
cos(a+b) = cosacosb - sinasinb
cos(a-b) = cosacosb + sinasinb
w'll get the desired answer.
To be solve
L.H.S = R.H.S
sinasinb = (cos(a-b)-cos(a+b)/2
as we know that cos(a+b) = cosacosb - sinasinb
sinasinb = (cos(a-b) - (cosacosb -sinasinb))/2
as we know that cos(a-b) = cosacosb + sinasinb
sinasinb = ((cosacosb + sinasinb) - (cosacosb -sinasinb))/2
sinasinb = (cosacosb + sinasinb - cosacosb + sinasinb)/2
sinasinb = (2sinasinb)/2
sinasinb = sinasinb
hence L.H.S = R.H.S