# Math Help - f(x), a & b values from Riemann Sum

1. ## f(x), a & b values from Riemann Sum

Hi everyone,

I'm very confused about how to do this problem, could someone please explain this to me?

Thank you

2. What you're being asked to do is to look at this Riemann sum & look for patterns.

It says to use A = 0 so we have some information already, you'll see how helpful that is in a second.

What we know so far:

$\int_{a} f (x)\,dx$

Okay, what is the definition of a Riemann sum?

$\lim_{x \to \infty} \sum_{i=1}^{n} f(x_i) \Delta x$

where;

$\Delta x = \frac{b - a}{n} \ and \ x_i = a + i\Delta x$

I could do the rest but I'll let you read this and see if you can figure the rest out on your own, if not I'll help you some more

3. Great, I think that helped. So it's:

f(x) = (8+x)^(1/2)
a=0
b=5

4. Yep

5. Thank you!

I hate to be a bother, but do you have any suggestions for this one?

Sorry, I guess I was just being impatient

f(x) = tan (x/4)
a = 0
b = pi/6

Thanks again for the help!

6. yeah, think about trigonometric limits. They are never like a = 2, b = 5, they are more like;

$\int_{\frac{\pi}{9}}^{\frac{7\pi}{6}} f (x)\,dx$

I'll give you a hint, you can take a = 0 in this one too & follow the same procedure, any problems just post back.

edit: no problem

7. I must have edited while you looked at it, but i figured it out! Thank you!