Expression Evaluation

[calvinmorris]

In Mathematica v10, this happens:

Questions:

Why is the derivative of y=f(x) not evaluated inside the integral to give 2x?

How can I re-write the input to cause the expression inside the integral to be evaluated prior to performing integration (definite)?

I’m trying to think back to my Lisp days for a hint, but it’s not helping

~CM

[fkampas (Frank Kampas)]

In[1]:= y[x_] = x^2;
a = 0;
b = 3;

In[4]:= Integrate[(1 + y'[x]^2)^(1/2), {x, a, b}]

Out[4]= 1/4 (6 Sqrt[37] + ArcSinh[6])

[calvinmorris]

Thanks, Frank. That was exactly the help I needed.

~CM