# More graphing calculator questions

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My son cannot figure out how to do "summations" on the 84+SE or the TI-Nspire - anyone know if it is possible? (He can do them on the nongraphing one)

Also I'm concerned that I do not really understand calculator use on the AP Calc exam....

He has taken some of his tests without any calculator at all, but he's still using his nongraphing calculator on homework. I see that on the problems in the Larson Calculus book, there is a little symbol for the calculator next to certain problems. Does that mean that he should not be using any calculator for the other problems (the ones without a graph symbol)? He's still using his nongraphing calculator for those and I'm thinking he might be too nongraphing calculator dependent. Any insights?

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I'll try the summation question first, but I'm working on a TI-89 Titanium, so it may be different. (My dd's TI-Nspire/84+ is off at college with her.)

For the summation of n^2 from n=1 to n=5, I would input

sum(seq(n^2, n, 1, 5))

and I'd get '55' for the answer. The commands 'sum' and 'seq' are in the Math-> List menu.

If I just wanted to sum up a group of numbers, I'd input

sum({1, 5, 6, 10})

and I'd get '22' for the answer.

Does that answer his question? Hopefully the same commands will work on one of his TI's.

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Joan - On the AP examination, there will be multiple choice and essay sections where he'll either be allowed to use a graphing (only) calculator, or else none at all. I'm not very familiar with the Larson text, so I can't answer specifically whether or not he should be using the scientific calculator on their homework problems. I would suggest that he start using a graphing calculator on the problems where one is suggested, though, so he'll be comfortable with it before May.

The four things he needs to be able to do on the graphing calculator for the test are:

1. Be able to produce a graph of a given function with a given viewing window. (They might have to reproduce the sketch on their paper.)

2. Solve an equation numerically (be able to use the 'solve' command on the TI for a given equation.)

3. Calculate the derivative of a given function at a specific given value.

4. Calculate the value of a definite integral.

For an example of how this might appear on the AB calculus exam, I pulled the following problem from the multiple-choice section of a released AP AB exam:

"A particle moves on the x-axis so that for time t >=0, its velocity is given by v(t) = 3 + 4.1 * cos(0.9*t). Find its acceleration when t = 4." (followed by five numerical answers).

The fastest way to the answer is to use procedure #3, inputting (on my TI-89):

d(3 + 4.1*cos(0.9*t),t) | t=4)

Here's another example from the same test:

"The velocity of a particle moving along the x-axis is given by the function v(t) = e^t + t* e^t. what is the average velocity of the particle from time t=0 to time t=3?" (followed by five numerical answers)

Again, the fastest way to answer is to use procedure #4, inputting (TI-89):

int(e^t + t*e^t, t, 0, 3) / 3.0 where I used "int" for the integral symbol.

Does that help?

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I'll try the summation question first, but I'm working on a TI-89 Titanium, so it may be different. (My dd's TI-Nspire/84+ is off at college with her.)

For the summation of n^2 from n=1 to n=5, I would input

sum(seq(n^2, n, 1, 5))

and I'd get '55' for the answer. The commands 'sum' and 'seq' are in the Math-> List menu.

If I just wanted to sum up a group of numbers, I'd input

sum({1, 5, 6, 10})

and I'd get '22' for the answer.

Does that answer his question? Hopefully the same commands will work on one of his TI's.

Yes it did! thank you so much!

Joan

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The four things he needs to be able to do on the graphing calculator for the test are:

1. Be able to produce a graph of a given function with a given viewing window. (They might have to reproduce the sketch on their paper.)

2. Solve an equation numerically (be able to use the 'solve' command on the TI for a given equation.)

3. Calculate the derivative of a given function at a specific given value.

4. Calculate the value of a definite integral.

What I'm finding out is that there is more to these words than I thought there was - it is a "code" that I don't know well yet. Eg I did not know there was a special command for "solving". Earlier my son told me he could solve an equation, but now I find out that he does not know how to use that command - but we're going to learn.

So I'm wondering about other "hidden" meanings. Maybe from your example below it is really related to speed of solution - that the most efficient way is through certain procedures? And that if you don't use the calculator to do these that you'll be too slow?

He was using the graphing calculator even for Precalc so he has learned something but maybe not in the most efficient way.

For an example of how this might appear on the AB calculus exam, I pulled the following problem from the multiple-choice section of a released AP AB exam:

"A particle moves on the x-axis so that for time t >=0, its velocity is given by v(t) = 3 + 4.1 * cos(0.9*t). Find its acceleration when t = 4." (followed by five numerical answers).

The fastest way to the answer is to use procedure #3, inputting (on my TI-89):

d(3 + 4.1*cos(0.9*t),t) | t=4)

Here's another example from the same test:

"The velocity of a particle moving along the x-axis is given by the function v(t) = e^t + t* e^t. what is the average velocity of the particle from time t=0 to time t=3?" (followed by five numerical answers)

Again, the fastest way to answer is to use procedure #4, inputting (TI-89):

int(e^t + t*e^t, t, 0, 3) / 3.0 where I used "int" for the integral symbol.

Does that help?

I see what you are saying about this and I'll have to see how he is doing this type of question. I'll get back to you.

Thanks Kathy!

Joan

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