Need Math Help

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  • ß?µ£ §mµ®ƒ
    University of Rochester
    • Aug 2003
    • 1012

    #1

    Need Math Help

    find the following trigonometric expression as an algebraic expression in terms of x show all work

    sin (2arcsinx)-cos(2arccosx)
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  • toyotaboy12
    e-tough

    • May 2003
    • 3663

    #2
    i am doign sign and cosign now. If you have a graphign calculator you should use that. I don't quite understand the problem you are trying to solve.
    I knew not what I did but am now edumacated

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    • ß?µ£ §mµ®ƒ
      University of Rochester
      • Aug 2003
      • 1012

      #3
      it wants an algebraic expression simplified i think cause after im suppose to plug the answer into x to solve sin(2arcsinx) = cos(2arccosx)
      • AGD "Yea well our intention is to
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      • bertmcmahan
        Not pop, it's all Coke
        • Jan 2002
        • 1960

        #4
        sin (2arcsinx)-cos(2arccosx)

        Haven't done strait trig in a while, so I can't remember what to do with the 2's, but the sin of the arcsin of something cancels. I.E. sin(arcsinX)=X. The problem wants you to get rid of the sines and cosines and all. Since there's no = sign I don't think you need to substitute. Just get rid of the 2's however you can and you can just cancel the trig parts. I think this is right. I know it works with log properties, but this could be different.
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        • gimp
          Registered User
          • Jan 2001
          • 2368

          #5
          Re: Need Math Help

          find the following trigonometric expression as an algebraic expression in terms of x show all work

          sin (2arcsinx)-cos(2arccosx)

          sin (2arcsinx)-cos(2arccosx) = ? doesn't it have to equal something? If you got rid of the 2s, it would be x-x. I think the 2 messes it up though

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          • bertmcmahan
            Not pop, it's all Coke
            • Jan 2002
            • 1960

            #6
            It's an expression, not an equation, so I'm pretty sure it doesn't have to equal something. The 2's make it do something weird, and I can't remember how to get rid of them.
            AIM-bertmcmahan
            My email:[email protected]
            My feedback thread
            Good traders: richie,Roguefactor,moufo48,845,brtncstm160,vf-xx

            Mags don't shoot darts... they shoot nails.
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            • deadeye9
              The other deadeye.
              • Jan 2003
              • 323

              #7
              The best I can do is:

              cos(2*arccos(x)) = 2*x^2 - 1

              and

              sin(2*arcsin(x)) = 2*x*sqrt(1 - x^2)

              The first comes from the trig identity:
              cos(2y) = 2*cos^2(y) - 1

              The second comes from the trig identity:
              sin(2y) = 2*sin(y)cos(y), therefore
              sin(2*arcsin(x)) = 2*x*cos(arcsin(x))

              Let y = ArcSin(x). We seek Cos(y). Then

              Sin(y) = x
              1 - (Sin(y))^2 = 1 - x^2
              (Cos(y))^2 = 1 - x^2
              Cos(y) = sqrt(1 - x^2)

              I got that last part from:
              http://mathforum.org/epigone/alt.mat...axrimwo/87fojb[email protected]
              Last edited by deadeye9; 03-29-2004, 06:27 PM.

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              • splatattack33
                i <3 pumps
                • Jul 2003
                • 442

                #8
                wow glad im still in 9th grade math

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                • sharpshooter1286
                  Registered User
                  • Feb 2003
                  • 1114

                  #9
                  wow glad im still in 9th grade math

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