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Mathematics
Mathematics
Problem
If
A
=
30
∘
A = 30^\circ
A
=
3
0
∘
, then prove that :
cos
3
A
=
4
cos
3
A
−
3
cos
A
\cos 3A = 4 \cos^3 A - 3 \cos A
cos
3
A
=
4
cos
3
A
−
3
cos
A
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