Prove that (1 - cos^2 x)(1 + cos^2 x) = 1

[Tinkermom]

(1 - cos^2 x)(1 + cos^2 x) = 1

If I "Foil" I get

1-cos^4 x or I could go this way... 1-cos^2 x = sin^2 x

not sure what to do.

 

[mmm4444bot]

(1 - cos^2 x)(1 + cos^2 x) = 1

We cannot prove that this equation is always true because it isn't.

If I "Foil" I get

1 - cos^4(x)

This is correct.

This expression equals 1 only when cos(x) is 1 or -1.

 

[Deleted member 4993]

(1 - cos^2 x)(1 + cos^2 x) = 1

If I "Foil" I get

1-cos^4 x or I could go this way... 1-cos^2 x = sin^2 x

not sure what to do.

Please check your problem - and post the complete problem. As posted - it cannot be correct.

 

[Tinkermom]

I'll have to ask my teacher about this one.