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A Maths C (Advanced Maths Integral Question)?

G'day.

Could someone please try and do this for me... Thanks

Evaluate: The Integral of (sin x/cos2 x - 5cos x+4)

*NB: The cos2 x, the 2 is a squared 2.

If you can, try and evaluate using partial fractions. But any standard Integral method that a Senior Maths student should know will be fine.

Thanks again.

3 Answers

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  • 1 decade ago
    Favorite Answer

    First consider the first term of the integrand.

    ∫ sinx(cos²(x)) dx

    You can evaluate this integral by letting u=cosx

    then

    du = -sinx dx

    If you multiply and divide by -1 and then substitute these values into the integral , you have

    -∫ du/u²

    which is the same as

    -∫ u^-2 du

    = u^-1 + C

    = 1/cosx + C = secx + C

    The other two terms are pretty straight forward. I come up with

    ∫ [ sin x/cos2 x - 5cos x+4 ] dx

    = sec(x) - 5sin(x) + 4x + C

  • PeterL
    Lv 4
    1 decade ago

    This is a simple antiderivative integral.

    Since the derivative of sinx is cosx and sinx/(cosx)^2=secxtanx

    Int { secxtanx -5cosx + 4 }

    = secx -5sinx +4x + C ANSWER

  • ?
    Lv 4
    5 years ago

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