Calculus Proof

[katie9426]

I have a calculus proof to do and no idea where to begin anyone who can give any help would be greatly appreciated!

Given: The cos(theta) = x/r and sin(theta) = y/r is the point of intersection of the terminal side of angle theta and a circle is centered at the origin of radius r.

Prove: sin squared (theta) + cos squared (theta) = 1

Hint: Square both sides of the equation defining sine and cosine and recall the equation for a cirlce centered at the origin of radius r.

Thanks![/list]

 

[pka]

Useally we define r such that: \(\displaystyle \L
r^2 = x^2 + y^2 .\)

 

[katie9426]

I understand that but I don't understand where to start my proof. I know I have to start with the given information, but I dont know where to begin to start the proof. Are you saying start by pluggin sin and cos into that equation?