Question

If a=60 degree verify that:
$\cos(2a) = \frac{1 - { \tan }^{2}a }{1 + { \tan }^{2} a }$

Answer 1

Hey !!

from LHS

cos2A = cos×2×60°

=> cos120° = cos(90° + 30° )

= -sin30° = -1/2

Now from RHS

1 - tan²A /1 + tan²A

=> 1 - tan²60°/1 + tan²60°

=> 1 - (√3²)/1 +(√3)²

=> 1 - 3/4

=>- 2/4 = -1/2 Prooved here RHS = LHS

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Hope it helps you !!!

@Rajukumar111
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