## The length of a curve

Determine

• #### Variant 1

circumference of a circle with radius $$r$$.

• #### Variant 2

the lenght of the curve $$y = x^{3/2}$$ for $$x \in [0,a]$$.

• #### Variant 3

the lenght of the curve $$y = \frac14 x^2 + \frac12 \ln x$$ for $$x \in [1,e]$$.