Question

how to find value of cos 15 with result cos A-B

Answer 1

Answer:

HEYA!!

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Cos 15 ° = Cos ( 45° - 30 ° )

Cos ( A- B ) = CosA CosB + SinA SinB.

Cos( 45° - 30° ) = Cos45. Cos30+ Sin45.Sin30

=

\frac{1}{ \sqrt{2} } \times \frac{ \sqrt{3} }{2} + \frac{1}{ \sqrt{2} } . \frac{1}{2}

\frac{ \sqrt{3} }{2 \sqrt{2} } + \frac{1}{2 \sqrt{2} } \\ \\ = \frac{ \sqrt{3} + 1 }{2 \sqrt{2} } \times \frac{2 \sqrt{2} }{2 \sqrt{2} } \\ \\ = \frac{2 \sqrt{6} + 2 \sqrt{2} }{8} \\ \\ = \frac{2( \sqrt{6} + \sqrt{2} )}{8} \\ \\ = \frac{ \sqrt{6} + \sqrt{2} }{4}

Answer 2

Answer:

HOPE IT WILL HELP YOU......