# How do you verify #(cos(x))(cos(x)) = 1-sin^2(x)#?

##### 1 Answer

We can rewrite the equation as

This is a fundamental equality for the trigonometric function, and its explanation is very simple: if you consider the unit circle, any point on the circumference

Since

I hope this image can help, since it shows that the sine and cosine of an angle form a right triangle whose hypotenusa is the radius.