Question

If A+B+C= and A = cooB cos C

then show that cotB cotC =0.5​

Answer 1

Answer:

Let us consider the problem.

Let

A+

B+

C=

180

0

degrees

Hence

A= 180

0

− (B+C)

Therefore

cosA= cosB+ cosC

Implies that

cos (180

0

−B−C) =

cosBcosC

implies that

−cos(B+C)= cosB.cosC

Implies that

−cosBcosC+ sinBsinC= cosB.cosC

Implies that

2cosBcosC= sinBsinC

Implies that

Hence

cotBcotC=

2

1

Answer 2

Answer:

If A+B+C= and A = cooB cos C

If A+B+C= and A = cooB cos Cthen show that cotB cotC =0.5