Trig Identity - Never Seen This Before

[carlodelmundo]

Homework Statement

http://carlodm.com/images/m.png

Homework Equations

sin² et + cos² et = 1

The identity above is foreign to me. Can anyone explain/have external links that explains this identity? I haven't seen anything like it and Google isn't showing anything useful.

Thanks

 

[carlodelmundo]

Nevermind. I realized it's just sin^2 (x) + cos^2 (x) = 1.

It looked weird. Same angles threw me off

 

[CFDFEAGURU]

That happens to all of us.

Thanks
Matt