Which integral represents the length of the curve y=f(x)y = f(x)y=f(x) from x=ax=ax=a to x=bx=bx=b?
∫ab1+[f′(x)]2dx\int_a^b \sqrt{1 + [f'(x)]^2} dx∫ab1+[f′(x)]2dx
∫ab1+[f(x)]2dx\int_a^b \sqrt{1 + [f(x)]^2} dx∫ab1+[f(x)]2dx
∫ab(1+f′(x))dx\int_a^b (1 + f'(x)) dx∫ab(1+f′(x))dx
∫abπ[f(x)]2dx\int_a^b \pi [f(x)]^2 dx∫abπ[f(x)]2dx