Question

find the value of cos 75° using identities. no spamm ....best ans will mark as brain lest​

Answer 1

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HERE IS YOUR ANSWER:-

$\cos( {75} ) = \cos(45 + 30) \\ \: = > \cos(45) \cos(30) - \sin(45) \sin(30) \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: ............ { \cos(a + b) = \cos(a) \cos(b) - \sin(a) \sin(b) } \\ \\ = > \frac{1}{ \sqrt{2} } \times \frac{ \sqrt{3} }{2} \: \: - \: \: \frac{1}{\sqrt{2} } \times \frac{1}{2} \\ \\ = > \frac{ \sqrt{3 } - 1 }{2 \sqrt{2} }$

Hence ,

$\cos(75) = \frac{ \sqrt{3} - 1 }{2 \sqrt{2} }$

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Answer 2

Answer:

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