Question

WITHOUT USING TRIGONOMETRIC TABLES EVALUATE COS SQUARE 25- SIN SQUARE 65​

Answer 1

Answer:

0

STEP BY STEP EXPLANATION:-

$\cos{}^{2} 25 - \sin {}^{2} (65 ) \\ since \: \cos(a) = \sin(90 - a) \\ therefore \: \cos {}^{2} (25) = \cos {}^{2} (90 - 25) = \sin {}^{2} (65) \\ = \sin^{2} (65) - \sin {}^{2} (65) = 0$

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