How do you prove tan (2x)/tan x=2?

1 Answer
Nghi N.
Nov 10, 2015

Prove tan 2x/(tan x) = 2

Ans: Wrong equation.

Explanation:

This trig equation is wrong.
Example: x = pi/4 --> tan x = 1 --> tan 2x = tan (pi/2) = infinity.
Another proof by using trig identity.
tan 2x = (2tan x)/(1 - tan^2 x)

(tan 2x)/(tan x) = 2/(1 -tan^2 x)
So, the expression omits the quantity: (1 - tan^2 x)

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