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anonymous

  • 5 years ago

How to find the value of sin[2cos^-1(-3/5)] without using calculator??

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  1. anonymous
    • 5 years ago
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    Let \[\cos^{-1}\frac{-3}{5} = A \implies \cos A = \frac{-3}{5} \implies \cos^2 A = \frac{9}{25}\] \[\cos^2 A + \sin^2 A = 1 \implies \sin A = \sqrt{1-9/25} = \frac{4}{5} \] We cant to find \[\sin 2A \] which is equal to \[2\sin A \cos A \]. Gogogogogogog

  2. anonymous
    • 5 years ago
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    Anwer is -24/25 and when i use with calculator it gives me that number...

  3. anonymous
    • 5 years ago
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    Cool; I did it without a calculator, using the method above, because I'm not a three year old baby.

  4. anonymous
    • 5 years ago
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    So what is your answer at then end of your method?? 4/5??

  5. anonymous
    • 5 years ago
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    ah so just plug 4/5 to the equation i got it thanks

  6. anonymous
    • 5 years ago
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    No.. The answer is 2 * sin A * cos A. And I told you sin A = 4/5 and cos A = 3/5.

  7. anonymous
    • 5 years ago
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    cos A = -3/5 ***

  8. anonymous
    • 5 years ago
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    Thank you

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