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Trigo!

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Ok, i did this maths trigo question, that says sinx-cos=2/3. I squared it on both sides to get sin2x=5/9 and did the sum. In the end i got two solutions, 16.9 and 73.1. However, when i substituted the answers back into the equation, only one of the 2 answers was correct! The other one didn't work out! Why is this so? I'm pretty sure both answers are correct, so what's going on? Please help!

  • Trigo! - ,

    You have done the right step, check your answers after you have squared each side of an equation.

    Take a simple case of
    x=-4
    square both sides,
    x²=(-4)²=16
    x=√16=±4
    check:
    x=-4 OK
    x=+4 not a solution.

    In your case, the solution of 73.126° is correct. The other one is false.

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