A few days ago
Anonymous

Trig homework help?

I understand the easier versions of these problems, but this stuff is just mind boggling me.

sin^4x – cos^4x = 1-2cos^2x

I can’t plug in a number to prove its right, I have to show how I can make each side equal each other. Simplest form should be 1 = 1. It includes all the random rules of stuff were like sin^2 + cos^2 = 1 and whatnot.

The easier problems I understand, but this is really hard.

Top 1 Answers
A few days ago
norcekri

Favorite Answer

First, the left side is the difference of two perfect squares.

The right side is a common trig identity (turn the 1 into sin^2+cos^2).

Does that get you started enough?

By the way, those aren’t “random rules of stuff”. They all derive algebraically from the Pythagorean Theorem and the base definitions of sine, tangent, secant, and “co-“something. If you can remember the basic definitions and the derivation methods, you can replace your rote memorization with a few handy techniques to rebuild the entire pantheon of theorems.

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