Answer:
A
Step-by-step explanation:
First, let's do the difference of two squares:
[tex](1-cos^4(\theta))=(1-cos^2(\theta))(1+cos^2(\theta))[/tex]
Note that [tex]sin^2(\theta)=1-cos^2(\theta)[/tex] (Pythagorean Identity)
Thus, we can substitute:
[tex]sin^2(\theta)(1+cos^2(\theta))[/tex]
Now, and I'm serious, you just have to use your creativity. After a while, you will find that:
[tex]sin^2(\theta)+cos^2(\theta)=1[/tex]
So:
[tex]1+sin^2(\theta)+cos^2(\theta)=1+1[/tex]
Thus, we have [tex]1+cos^2(\theta)=2-sin^2(\theta)[/tex]
Now, we can substitute:
[tex]sin^2(\theta)(2-sin^2(\theta))=2sin^2(\theta)-sin^4(\theta)[/tex]
