Results 1 to 3 of 3

Math Help - Three Precalculus Problems to Check Answers

  1. #1
    Junior Member
    Joined
    Dec 2008
    Posts
    34

    Smile Three Precalculus Problems to Check Answers

    3/18/09

    I have done three problems and need verification of my answers.

    1. Write the rectangular equation x=3 in polar form. My answer: rcostheta=3

    2. Simplify {(sq. root of 3) + i}^4 My answer: 8 + 8(sq.root3i

    3. Find (costheta+isintheta)^2 My answer: cos^2theta - isin^2theta

    Thank you in advance for your help.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    10,973
    Thanks
    1012
    Quote Originally Posted by Joanie View Post
    3/18/09

    I have done three problems and need verification of my answers.

    1. Write the rectangular equation x=3 in polar form. My answer: rcostheta=3

    2. Simplify {(sq. root of 3) + i}^4 My answer: 8 + 8(sq.root3i

    3. Find (costheta+isintheta)^2 My answer: cos^2theta - isin^2theta

    Thank you in advance for your help.
    The first two are correct.

    For the third

    (\cos{\theta} + i\sin{\theta})^2 = \cos^2{\theta} + 2i\cos{\theta}\sin{\theta} - \sin^2{\theta}.

    Remember that

    \cos^2{\theta} - \sin^2{\theta} = \cos{2\theta} and 2\cos{\theta}\sin{\theta} = \sin{2\theta}.

    So (\cos{\theta} + i\sin{\theta})^2 = \cos{2\theta} + i\sin{2\theta}.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Dec 2008
    Posts
    34

    Smile Thanks for the Help

    Your comments were very helpful. Thanks so much.

    Joanie
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. A few Precalculus function problems
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: April 17th 2011, 11:58 AM
  2. Replies: 3
    Last Post: November 26th 2008, 04:56 PM
  3. Replies: 7
    Last Post: February 9th 2008, 08:01 AM
  4. Two Precalculus Problems
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: February 7th 2008, 03:47 PM
  5. mathematical models(precalculus) problems
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: November 22nd 2006, 08:34 PM

Search Tags


/mathhelpforum @mathhelpforum