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anonymous

  • one year ago

PLEASE HELP ME!!! I JUST NEED TO KNOW HOW TO DO THIS!! Verify the identity. cos(4u)=cos^2(2u) - sin^2(2u)

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  1. anonymous
    • one year ago
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    I made this trig sheet. http://learnix.net/wordpress/wp-content/uploads/Trig-Cheat-Sheet-1.4.pdf Can you see an identity on it that might fit this situation?

  2. anonymous
    • one year ago
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    I'm really not sure how this is done. This is why I am asking how it can be done

  3. anonymous
    • one year ago
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    check out on my sheet where it says Angle Sum and Difference Do you see the cosine one, which is second from top?

  4. anonymous
    • one year ago
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    yes? Could you please tell me how to do it?

  5. anonymous
    • one year ago
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    like what steps would I take?

  6. anonymous
    • one year ago
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    So what do we need to do to make cos(4u) to look like cos(x+y) where x and y are anything. Sorry for the delayed response too.

  7. anonymous
    • one year ago
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    i don't know, please just explain to me

  8. anonymous
    • one year ago
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    okay, so we can rewrite cos(4u) as cos(2u+2u) right?

  9. anonymous
    • one year ago
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    yes

  10. anonymous
    • one year ago
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    According to my cheat sheet you follow the right hand side of the equation now. Can you do that?

  11. anonymous
    • one year ago
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    no, please just show me how to do it. I'm a visual learning

  12. anonymous
    • one year ago
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  13. Loser66
    • one year ago
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    \(cos (4u) = cos (2u+2u)\) ok?

  14. anonymous
    • one year ago
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    okay, why?

  15. Loser66
    • one year ago
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    not yet, be patient

  16. anonymous
    • one year ago
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    you got it

  17. Loser66
    • one year ago
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    cos (a+b) = cos acosb - sina sinb now, apply to your problem with a = 2u and b = 2u also you have : \(cos (4u) = cos (2u+2u) = cos (2u)cos (2u) - sin(2u) sin(2u) = cos^2 (2u) -sin^2 (2u)\) dat sit.

  18. anonymous
    • one year ago
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    Thank you!!

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