Originally Posted by

**Riazy** Hi guys,

**Problem: A curve is given in polar coordinates by r = fi^2 between -pi <= fi =< pi**

**Determine the length of the curve.**

**My progress:**

**I recall a formula my teacher has given us: L(x) = $(using given limits of integration) SQRT (h^2(fi)) + [h'(fi)]^2) d(fi)**

**= This would give me **

**$SQRT (fi^2)^2 + (2fi)^2 d(fi)**

**So far so good, right?**

**$SQRT (fi)^4 + 4fi^2 d(fi)**

**I think Variable substititution would be good here**

**U = (fi)^4 + 4fi^2 d(fi)**

**DU/D(fi) = 4(fi)^3 + 8fi**

**Hmm How can i complete this?**

**could someone help me in detail, thanks**