beginner question / formula

[ashlee]

http://img529.imageshack.us/img529/9808/helpz.png

pretty new to c programming (in a class) so i've been running through the chapters to figure this one but but not really sure.

would this be float, a, p, i, n, mortgage;?

and mortgage = the formula?

[Elysia]

What do you need to know exactly?
It looks like you've been given an assignment of creating a program that calculates something and prints out the result. So you need to create variables, do the calculation and print the result.

[Adak]

I would use floats ONLY when, for some reason, you can't use doubles for your floating point data type.

Yes, a = monthly payment, just like the picture shows.

work inside the parentheses first, with multiplication and division having priority over addition and subtraction.

Then repeat that, after you have simplified the inner, parenthesized sets.

Since this is basic math, I doubt you'll find much in your programming book, to help you.

[nonoob]

That diagram is misleading. The author meant to say

(1+i/12) to-the-exponent (-12n)

[Babkockdood]

I would look at arithmetic operators and math.h functions.

[ashlee]

int main ()
{
double a, p, i, n, total;

printf ("Enter monthly mortgage payment \n");
scanf ("%f", &a);
printf ("loan amount? \n");
scanf ("%f", &p);
printf ("annual interest rate? \n");
scanf ("%f", &i);
printf ("how many years? \n");
scanf ("%f", &n);

is what i have now
should i split up these calculations x= p(i/12)/(1-(1+i/12)(-12n)? and then the answer to that cout<<pow(x,12)<<endl;
and the answer to that times n?

[Elysia]

Are you using C or C++?

[ashlee]

regular c, sorry did not mean to have the int main there

[Elysia]

cout is C++. So is endl.

[ashlee]

cout is C++. So is endl.

oh okay. guess this tutorial is no good then.

[ashlee]

so is it just pow(-12) ?

[Elysia]

pow takes two arguments: the base and the exponential.

[ashlee]

i guess my question is is how do i put this into c?
do i split up this long formula into parts such as first do the beginning... then take that and put it to the power of -12.. then take that and times it by n? or would i just put the whole thing in at once such as
x= p(i/12)/(1-(1+i/12)*pow(-12)*n.
just need some direction that i know im doing something right before i spend hours doing trial and error. (man i wish we started with something easier)

[Elysia]

You can do both. You can treat C as a mathematical language.
+ - * and / work just as in math. So you can write that formula directly. Exponentials are handled by pow.
Variables must be created in C. So you define them first. Then you can assign them values and use those values in your calculation.
The expression

x= p(i/12)/(1-(1+i/12)*pow(-12)*n

is perfectly fine if you've defined x, p and i (and filled them with appropriate values).

[ashlee]

thank you for your help