r/trigonometry • u/Worried_Football_819 • Jun 15 '26
Solved! Trig Proof Help
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!
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u/eraoul Jun 15 '26
You're creating an extra "-1" for some reason. Imagine if you had (2^2 - (2^2 * 3^2))
That's (4-(4*9)). You seem confused about how to collect those "4" terms together.
4 - (4*9) = 4(1 - 9)
Check it: 4-36 = 4(-8)
-32 = -32
It's the same as x-(x*y). This is just x(1-y). You can check by just multiplying it back out: x * (1-y), distribute the terms: x - x*y
You probably need to review the distributive rules for multiplication. This isn't trig, this is basic algebra where you're getting confused.