trigonometic identities

[neelam]

Write tanxcos^3x in terms of sinx . I did sinx/cox *cos^3x. This allowed me to cancel the cosx to get = sinxcos^2x. This gave me sinx(1-sin^2x). I then expanded the brackets to get my answer sinx-sin^3x. This is wrong, the answer is 1-sin^2x. Any ideas of where I have gone wrong?

 

[Deleted member 4993]

Write tanxcos^3x in terms of sinx . I did sinx/cox *cos^3x. This allowed me to cancel the cosx to get = sinxcos^2x. This gave me sinx(1-sin^2x). I then expanded the brackets to get my answer sinx-sin^3x. This is wrong, the answer is 1-sin^2x. Any ideas of where I have gone wrong?

As posted, you have solved the problem correctly.

Either your text-book answer is wrong or you are looking at the solution of a different problem.