Help in Solving a problem using F.T.C

[lilypeach]

Hi, here's my problem



Use the Fundamental Theorem of Calculus to evaluate the definite integral.
from the int. of -1 to 1, with the function being 5/x^2+1

= 5 int. 1/x^2+1
= 5 int. tan^(-1)(x)
= 5 x tan^-1(x)
Plug in 1 and -1...subtract...= 450, except it's wrong.

I've gotten as far as 5 int. tan^-1(x), and I get 450 once I plug in the limits, Am I missing anything?

 

[LCKurtz]

Hi, here's my problem
Use the Fundamental Theorem of Calculus to evaluate the definite integral.
from the int. of -1 to 1, with the function being 5/x^2+1

= 5 int. 1/x^2+1

You need parentheses if you mean an integrand of 1/(x²+1)

= 5 int. tan^(-1)(x)

And if you have taken the antiderivative, you shouldn't still have the "int" in front.

= 5 x tan^-1(x)

And where did the x in front come from?

Plug in 1 and -1...subtract...= 450, except it's wrong.

I've gotten as far as 5 int. tan^-1(x), and I get 450 once I plug in the limits, Am I missing anything?

That last antiderivative, somehow, is actually correct. But remember in derivatives and integrals of trig function, x is always in radians.

 

[lilypeach]

excellent, got it.

Thanks a million.