1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Ax = x cos(angle)

  1. Nov 14, 2014 #1
    In physics we use the formulas Ax = x cos(angle) and Ay = y sin(angle) to find the x or y component of a vector. How do these formulas work, and what all can they be used for?
  2. jcsd
  3. Nov 14, 2014 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Have you studied trigonometry?
  4. Nov 14, 2014 #3
    I'm taking my first year of high school physics and algebra/trig this year so I don't know too much about trigonometry as of now.
  5. Nov 14, 2014 #4


    User Avatar

    Staff: Mentor

    Many physical quantities have both a magnitude and a direction: velocity, acceleration, force, momentum, etc. We call these vector quantities. In everyday language it's most natural to describe them using the magnitude and either one angle (for two-dimensional motion) or two angles (for three-dimensional motion). However, many mathematical operations (like adding two vectors) are easier if you use x- and y- (and possibly z-) components. So you spend a lot of time in intro physics courses learning how to convert between magnitude+angle(s) and components. That's where the trigonometry comes in.

    If you need something to supplement your textbook for the mathematical details, try this:


    It does assume that you already know basic trig stuff like the definitions of sine and cosine.
  6. Nov 14, 2014 #5
    If your question is related to basic trig:
    Given a right triangle...

    sin(angle) = opposite_length / hypotenuse_length
    so, multiplying both side by hypotenuse_length gives us:
    opposite_length = hypotenuse * sin(angle)
    Thus, Ay = A sin(angle)

    cos(angle) = adjacent / hypotenuse_length
    so, multiplying both side by hypotenuse_length gives us:
    adjacent_length = hypotenuse_length * cos(angle)
    Thus, Ax =A cos(angle)

    In many physics problems you'll find that the hypotenuse_length is represented by velocity or force.

    Here is couple more google links 1, 2, ...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook