Question

in aABC write cos {b+c}/2in terms of A​

Answer 1

Answer:

Step-by-step explanation:

In the given ΔABC ,

cos(b + c) = 90° [as, ∠a is 90° ]

therefore cos 90° = cos A

Answer 2

Answer:

$a + b + c = 180 \\ b + c = 180 - a \\ \ \cos( \frac{b + c}{2} ) = \cos( \frac{180 - a}{2} ) \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \cos(90 - \frac{a}{2} ) \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \sin( \frac{a}{2} )$

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