Question

If cos Q=√21/5,then find the value of 10+10 cot 2 Q
please answer​

Answer 1

Answer:

(170+80√21)/17

Step-by-step explanation:

Using Cos2Q = CosQ×CosQ-SinQ×SinQ

And then Sin²Q = 1 - Cos²Q

Cot2Q = Cos2Q/Sin2Q