Part of CALC-10 — Integration: Advanced Techniques & Reduction

Integral of 1/(a+b*sin(x)) and 1/(a+b*cos(x))

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For integral dxa+bsin(x\frac{dx}{a + b*sin(x}): Use t = tanx2\frac{x}{2}. sin(x) = 2t1+t2\frac{t}{1+t^2}, dx = 2dt1+t2\frac{dt}{1+t^2}. Integral = integral 2dt/[a(1+t2t^2) + 2bt] = integral 2dt/[at2at^2 + 2bt + a]

Complete the square in denominator and integrate:

  • If a2a^2 > b2b^2: result involves arctan
  • If a2a^2 < b2b^2: result involves logarithm
  • If a2a^2 = b2b^2: simplifies directly

For integral dxa+bcos(x\frac{dx}{a + b*cos(x}): Same Weierstrass substitution. cos(x) = 1t2(1+t2)\frac{1-t^2}{(1+t^2)}. Integral = integral 2dt/[(a+b) + (a-b)t2t^2]

Result when a > b > 0: integral dxa+bcos(x\frac{dx}{a + b*cos(x}) = (2/sqrt(a^{2-b}^2)) * arctan[sqrt(ab(a+b)\frac{(a-b}{(a+b)}) * tanx2\frac{x}{2}] + C

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