Expert: Ahmed Salami - 4/8/2011

Question
Hello, how would i convert an equation of the form rcos(at +Theta) into polar form? i have some specific questions but im trying not to write the actual equation but my above notation looks confusing. Here is an actual question: 9cos(2t-7PI/8). I think the answer is 9 with an angle of -7PI/8 but that seems to easy!Thanks!

Answer
Hi Jay,
An equation of the form r = f(θ) is already in polar form so i dont quite get you.
Anyway, in cartesian form, y = f(x) and the conversion between forms is generally
x = rcosθ
y = rsinθ
or
r = √(x² + y²)
θ = arctan(y/x)

If you dont mind further reading;
http://en.wikipedia.org/wiki/Polar_coordinate_system

Regards