Explanation
∫π/40sinθ+cosθ9+16sin2θdθ
Let sinθ−cosθ=t
∴(cosθ+sinθ)dθ=dt
=∫0−1dt9+16(1–t2)(∵t2=1–2⋅sinθ⋅cosθ)
=∫0−1dt25–16t2
=116∫0−1dt(54)2–t2
=116×12×54[ln|54+t54–t|]0−1
(∵∫1a2–x2dx=12aln|a+xa–x|+c)
=140[ln|1|−ln|1494|]
=140ln9=ln320
∴∫π/40sinθ+cosθ9+16sin2θdθ=ln320.
∫π20√cosxsin5xdx ∫π20√cosx(sin4x)sinxdx −∫π20√cosx(1−cos2x)2dcosx −[∫π20√cosxdcosx+∫π20√cosxcos4xdx−2∫π20√cosxcos2xdx] −[23cos32x∫π20+211cos112x∫π20−2(27)cos72x∫π20] =−[23(−1)+211(−1)−2(27)(−1)] =64231
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