Question

a=4 b=5 c=7 can find cos B/2​

Answer 1

Given :-

In ️ ABC, a = 4, b = 5 and c = 7.

To find :-

$cos \frac{B}{2}$

Formula used :

1. Perimeter, 2s = a + b + c

2.

$cos \frac{B}{2} = \sqrt{ \frac{s(s - b)}{ac} }$

Solution :-

Perimeter, 2s = a + b + c

2s = 4 + 5 + 7

2s = 16

=> s = 8

Now,

$\small\bold\red{cos \frac{B}{2} = \sqrt{ \frac{s(s - b)}{ac} } } \\ \small\bold\red{ = \sqrt{ \frac{8(8 - 5)}{4 \times 7} } } \\ \small\bold\red{ = \sqrt{ \frac{6}{7} } }$

Answer 2

Answer:

he said you correct answer......