Thread: questions on some concepts

I know some equations are true, like

(sin A)^2 + (cos A)^2 = 1

sin (90 - A) = cos A

cos (90 - A) = sin A

but does these equations have any limitation on the angle A?

can A be any real angle?

thanks!

Originally Posted by kenny1999

I know some equations are true, like

(sin A)^2 + (cos A)^2 = 1

sin (90 - A) = cos A

cos (90 - A) = sin A

but does these equations have any limitation on the angle A?

can A be any real angle?

thanks!

I wouldn't be true if it was not applicable to all real values of A.