Question

find the value of cos 7 1/2°​

Answer 1

Consider the given function

$\cos(7 \frac{1}{2} )$

$\cos {15}^{0}$

Therefore,

$\cos {15}^{0} = \cos( {45}^{0} - 3 {0}^{0} )$

$\cos {15}^{0} = \cos4 {5}^{0} \cos {30}^{0} = \sin(4 {5}^{0} \sin {30}^{0}$

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

$\frac{ \sqrt{3} }{2 \sqrt{2} } + \frac{1}{ \sqrt{2} }$

$\frac{ \sqrt{3 + 1} }{2 \sqrt{2} }$

Hence this is the answer

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