The integral 80∫0π4(sinθ+cosθ9+16sin2θ)dθ is equal to : [2025]
(1)
Let I=80∫0π4(sinθ+cosθ)dθ(9+16sin2θ)
=80∫0π4(sinθ+cosθ)dθ9+16(1–1+2sinθcosθ)
=80∫0π4(sinθ+cosθ)dθ25–16(sinθ–cosθ)2
Put sinθ–cosθ=t ⇒ (cosθ+sinθ)dθ=dt
When θ=0, t=–1 and θ=π/4, t=0.