Question

6. The value of cot2(cot-13 + cot-17 + cot'13 +
cot'21) is equal to ​

Answer 1

Step-by-step explanation:

tan

−1

(

n

2

+n+1

1

)

=tan

−1

[

1+x(n+1)

(x−1)−n

]

=tan

−1

(n+1)−tan

−1

(n)

n=1,tan

−1

(2)−tan

−1

(1)

n=2,tan

−1

(3)−tan

−1

(2)

n=3,tan

−1

(4)−tan

−1

(3)

=tan

−1

(∞)−tan

−1

(1)

=

2

π

−tan

−1

(1)

=cot

−1

(1)