Question

A=30 then prove that cos A= 4 cos3 A - 3 Cos A

Answer 1

Heya

_______________________________

Your Question is wrong

Question should be like this

3 Cos A = 4Cos³ A - Cos 3A

L.H.S

3Cos (30) = 3√3/2

R.H.S

4× Cos³ (30) - Cos ( 90)

=>

4 × ( √3/2)³ - ×(0 )

=>

{12√3 /8 }

=>

√3 { 3/2 }