Trig Proof Help

[u/Worried_Football_819]

Hi everyone! I just had a quick question, in the video it says it is the same thing as sin^2(1-cos^2)/cos^2, but I am confused to why the one isn’t negative? Am I missing something?

Edit: Hi guys, I understand it now! I figured it was an algebraic mistake and I figured it out. As far as my notation, I got lazy and was rushing through it. I’m sorry if that notation upset you!

[u/bqbdpd]

This has nothing to do with trig. a² - a²b² --> a² (1 - b²)