Verify that 2A = 1 - 2 A/1 + 2 A for A = 30° .

CBSE Class 10 Maths PYQ · Trigonometry · Specific Angles Expression · 2 Marks · March 2025 · Basic

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1202 Marks · March 2025 · Basic
Verify that $\cos 2A = \frac{1 - \tan^2 A}{1 + \tan^2 A}$ for $A = 30^\circ$.
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$LHS = \cos 60^\circ = \frac{1}{2}$
$RHS = \frac{1 - \tan^2 30^\circ}{1 + \tan^2 30^\circ} = \frac{1 - \frac{1}{3}}{1 + \frac{1}{3}} = \frac{1}{2} = LHS$
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