trig

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use sum or difference identities to find the exact value of the trigonometric function: tan 345

please show work, i cant figure out what im doing wrong!

  • trig -

    tan(345)?

    Tan(2*345)=tan(690)=tan(720-30)=tan(-30)

    tan(2*345)= 2*tan(345)/(1-tan^2(345)

    lets call tan(345) Y

    tan(-30)=2y/(1-y^2)

    Call Tan(-30) X
    x-XY^2=2Y
    XY^2+2Y-x=0

    use the quadratic to solve for y in terms of X

    (tan(-30)=-1/sqrt3)

  • trig -

    prove that tan20 tan30 tan40 = tan 10

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