Okay I am getting lost.

I have the IS curve

Y= (1/ (1-c-d))* ( c0-cT+I-fi+G)

Given a change in interest rate i the output is going to change in this way:

delta Y =[ (- f)/( 1-c-d) ]* delta i

given " i" on the y axis and Y on the x axis, if "f" is big/small the curve is steeper/flatter? Why? What is the right "couple" and why? I tried with numbers and calculator but what is the angle I shall consider?

Thank you so so much.