# How do you prove that tan^2A+cot^2A=1 is not an identity by showing a counterexample?

Dec 23, 2016

#### Answer:

It makes A unreal.

#### Explanation:

This is another form of ${\sin}^{2} \left(2 A\right) = \frac{4}{3}$ that implies

$| \sin \left(2 A\right) | = \frac{2}{\sqrt{3}} > 1.$

So, A is unreal.