Which of the following integrals are equivalent to ∫01dx1+x2\int_0^1 \frac{dx}{1+x^2}∫011+x2dx?
∫0π/4sec2(θ)⋅dθsec2(θ)\int_0^{\pi/4} \sec^2(\theta) \cdot \frac{d\theta}{\sec^2(\theta)}∫0π/4sec2(θ)⋅sec2(θ)dθ
∫01dt1+t2\int_0^1 \frac{dt}{1+t^2}∫011+t2dt
∫0π/41 dθ\int_0^{\pi/4} 1 \, d\theta∫0π/41dθ
π4\frac{\pi}{4}4π