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Question: In \(\triangle A B C\)if \(a = 16 , b = 24\) and \(c = 20\)then \(\cos \frac { B } { 2 } =\)...

In △ABC\triangle A B Cif a=16,b=24a = 16 , b = 24 and c=20c = 20then cos⁡B2=\cos \frac { B } { 2 } =

A

3/4

B

1/4

C

1/2

D

1/3

Answer

3/4

Explanation

Solution

2s=a+b+c2 s = a + b + c; cos⁡B2=30×6320=34\cos \frac { B } { 2 } = \sqrt { \frac { 30 \times 6 } { 320 } } = \frac { 3 } { 4 }.