How does the TI-84 find integrals? Are they just estimates?

Question

myininaya · Answer

So you want to know how ti-84's are programmed?

myininaya · Answer

I would actually have to google that.
I will type what algorithms are ti-84 programmed with to find integrals

myininaya · Answer

Sounds like they take a numerical approach to the answer so must of the time you will probably get an estimate http://www.tc3.edu/instruct/sbrown/ti83/integr.htm

anonymous · Answer

Just used wolfram to check and either they take the same approach or the ti has a very close estimate

anonymous · Answer

http://www.wolframalpha.com/widgets/view.jsp?id=8ab70731b1553f17c11a3bbc87e0b605

anonymous · Answer

I typed in (30000e^(-0.15x)*2*sqrt(1-x^2))dx

anonymous · Answer

Can you help me with a problem ? @myininaya

myininaya · Answer

i can try
what is your question

anonymous · Answer

attachment

anonymous · Answer

I know how to get the right answer, but before learning how to get the right answer I tried it and I think my way should also give the right answer...

anonymous · Answer

Here is how the book solves these types of problems:

anonymous · Answer

Are you following me so far?

myininaya · Answer

i think there is a formula for this if i'm not mistaken
$$2 \pi \int\limits_{0}^{1}r p(r) dr $$

anonymous · Answer

Yes thats what the book says

anonymous · Answer

But... the way I did it seems like it should work too

myininaya · Answer

how did you do it

anonymous · Answer

The way i did it was by taking the area of a vertical slice and multiplying it by the population density which would give the amount of people

anonymous · Answer

similar to the way the book does it but instead of ring slices i just used vertical ones

anonymous · Answer

so the area of a tiny slice would be 2sqrt(1-x^2)(delta x)

anonymous · Answer

but my answer is off by about 9180.514

myininaya · Answer

can you draw it for me what you did

anonymous · Answer

|dw:1405629558140:dw|