# Can anyone please explain what is wrong with this equation?

#### skiddy

##### New member
Can anyone please explain what is wrong with this equation:

r=0.8+1.6*sin(6*t)

theta=2*t

phi=0.6*pi*sin(12*t)

im using it in spherical coordinates, i keep trying to alter the equation about to get it to work, but keep failing!! Sometimes it fails due to the 'sin' comment

Change the r to rho - this will work.

Ed

what shape are you trying to plot? those equations don't seem right.....

try this set.....

rho = .8 + 1.6 * sin(6 *theta)

theta = 360 * t

phi = 0.6 * sin(12 *theta)

is this the shape you're looking for?

i forgot an explanation.... your range is way too small. you are setting to be from 0 to 2. do you happen to have a picture of what you want it to look like?

you can just use this one also....

rho = 0.8 + 1.6 *sin(6*t* 300)

theta = 2* t * 300

phi = 0.6 * pi * sin(12*t*300)

Skiddy-

Not long ago I tried modeling a sinusoidal cooling fin using the SIN(x) function. As mathematics hoes, I at first assumed that the argument x had to be in radians. I tried and tried and couldn't get it to work. Finally, I tried converting the argument x to degrees ala (180x/pi). It worked!