Question

if theta =30° verify the following :- (a) cos 3 theta° = 4 cos ^3 theta - 3 cos theta (B) sin 3 theta° = 3 sin theta - 4 sin ^3 theta

Answer 1

a) cos(3×30°)=4cos^3(30°)-3cos(30°)
cos 90°=4cos^3(30°)-3cos(30°)
0=4(_/3÷2)^3-3×_/3÷2
0=(12_/3)/8-(3_/3)/2
0=(3_/3)/2-(3_/3)/2
0=0

b) sin(3×30°)=3sin(30°)-4sin^3(30°)
1=3×1/2 - 4×1/8
1=3/2-1/2
1=2/2
1=1

Hence all proved..
Actually it a trigonometric formula in class 11.

PLZ MARK IT AS BRAINLIEST..

Answer 2

hope this will help you