Where does the pythagorean identity sin2 θ + cos2 θ = 1 come from? how would you use it to find the sine cosine and tangent values of the angle?

Consider right triangle ABC wit hright angle C. Then by the Pythagorean theorem,

Divide this equality by

Note that

Then

Suppose that you know the sine of the angle, then tha cosine of the angle can be determined as

If you divide the equality by the you get

what is the original number? you forgot to add it.

irrational, cannot