# Coordinate Systems Transformation(Rectangular to Cylindrical)

I am new to this subject:

• Cartesian, Cylindrical and Spherical coordinate system.
• Coordinate System Transformation

I have this example problem that I cant get the right answer.

Transform to cylindrical coordinates:

(a) $F=10ax -8ay +6az$ at point $P(10, -8, 6)$.

One of my problem is

• I dont know when to use the dot product or matrix transformation equation. Should I just solve for the cylindrical variables $(\rho,\phi,z)$ or use the dot product/matrix form to transform to another coordinate system?

I tried solving it using the equations but I cant get the correct answer. The correct answer is $12.81a\rho + 6az$

• The given answer makes no sense. Evaluating a function at a given point gives a value. Plugging $P=(10,-8,6)$ into $F$ gives $72a$. – Christian Blatter Jul 22 '15 at 18:13
• What is $a$? Is it some arbitrary number? Or are you trying to write a subscript? – Muphrid Jul 24 '15 at 0:03