TI-83 Equation Solver help?

Ok so i have a math final coming up and i was wondering what is wrong with my equation solver We've been studying projectiles and i have this equation 0=(D * tan(a) -4.9 * D^2 / V^2 / cos(a) ) ^2 this then shows D= A= V= from there you can put values into d,a,and v to solve for one another.... show more Ok so i have a math final coming up and i was wondering what is wrong with my equation solver

We've been studying projectiles and i have this equation

0=(D * tan(a) -4.9 * D^2 / V^2 / cos(a) ) ^2

this then shows

D=
A=
V=

from there you can put values into d,a,and v to solve for one another.

Each time i have attempted i have been giving this message:

ERR : NO SIGN CHNG

i am just wondering if i put the equation in wrong or whats going on

thanks for your help
3 answers 3