# Prove (asin t - bcos t) ^2 (b sint t + a cost t)^2 = a^2 + b^2

• Feb 21st 2011, 05:12 PM
ilyhyunbin
Prove (asin t - bcos t) ^2 (b sint t + a cost t)^2 = a^2 + b^2
(asin t - bcos t) ^2 (b sint t + a cost t)^2 = a^2 + b^2

I tried, believe me.
Its too difficult.
• Feb 21st 2011, 08:25 PM
mr fantastic
Quote:

Originally Posted by ilyhyunbin
(asin t - bcos t)^2 + (b sint t + a cost t)^2 = a^2 + b^2

I tried, believe me.
Its too difficult.

The red plus sign I added is not unimportant. Now expand and simplify using the Pythagorean Identity.
• Feb 21st 2011, 09:13 PM
topsquark
Maybe it's just because I'm up too late. What the heck are "b sint t" and "a cost t?"

-Dan
• Feb 22nd 2011, 03:08 AM
mr fantastic
Quote:

Originally Posted by topsquark
Maybe it's just because I'm up too late. What the heck are "b sint t" and "a cost t?"

-Dan

I believe that a and b are constants that are multiplying the sin(t) and cos(t) functions.
• Feb 22nd 2011, 10:05 AM
topsquark
Well, the OP doesn't seem to have a problem with it (or hasn't come back yet.) My problem is that extra "t" in "sint t" and "cost t". Sorry for not being more clear.

-Dan