Question

(ii) cot 2A
col? A-1
2 cot A​

Answer 1

cot(A+B)=

cotB+cotA

cotAcotB−1

=

a

c

+

ac

ac

.

a

c

−1

=

c

(1+a)

(c−1)

a

=

c

(1+a)

(a

2

+a)

a

[∵c=a

2

+a+1,∴c−1=a

2

+a]

=

c

a

a

=

c

a

3

=cotC

∴A+B=C