Question:

Prove that cos^4A - sin^4A= cos 2A?

by  |  earlier

0 LIKES UnLike

Prove that cos^4A - sin^4A= cos 2A?

 Tags:

   Report
Answer The Question I've Same Question Too

2 ANSWERS

Sort By: Date  |  Rating

  1. cos^4A -sin^4A =(cos^2 -sin^2A)(cos^2 A +sin^2A) =

    cos^2A -sin^2A =cos2A (a double angle identity)


  2. cos^4 A - sin^4 A = (1 + cos 2A / 2)^2 - (1 - cos 2A / 2)^2       [double angle formulae]

    = (1 + 2 cos 2A + cos^2 2A - 1 + 2 cos 2A - cos^2 2A) / 4

    = 4 cos 2A / 4

    = cos 2A
You're reading: Prove that cos^4A - sin^4A= cos 2A?

Question Stats

Latest activity: earlier.
This question has 2 answers.

BECOME A GUIDE

Share your knowledge and help people by answering questions.
Register Now
Unanswered Questions