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ewkmath

  • 2 years ago

what is X when 2sin^2(X)+9cos(X)+3=0

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  1. Shadowys
    • 2 years ago
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    have you subbed \(\sin^2 x x = 1-\cos^2 x\) into the eq to simplify it into a quadratic eq?

  2. ewkmath
    • 2 years ago
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    no i haven't but i'll try it out right now thanks :)

  3. Shadowys
    • 2 years ago
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    u r welcome. The solution should be trivial after the substitution. :)

  4. ewkmath
    • 2 years ago
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    I tried it but i still don't get it..

  5. Shadowys
    • 2 years ago
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    subbing, you should get, \(2-2\cos^2 x + 9 \cos x +3=0\) which equals, \(-2\cos^2 x + 9 \cos x +5=0\) let u = cos x the equation becomes \(-2u^2 + 9 u +5=0\) which is a quadratic equation of u. You can use the general formula to solve for u.

  6. ewkmath
    • 2 years ago
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    thanks o much.. i really appreciate it

  7. Shadowys
    • 2 years ago
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    you're welcome :)

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