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!

Homework Help: Need some clarification in regards to trigonometry

  1. Jun 4, 2008 #1
    Need some clarification in regards to trigonometry....

    1. The problem statement, all variables and given/known data

    For some reason, I am not seeing the cause of this. In attached problem 1, the Forces of x are described with a cos while forces of y are described with sin. In the second problem, the forces of X use sin and the forces of y use cos...... What am I missing here? Is there a certain topic I can review? Is it because of the quadrants they are in? the triangle they make (I would think obviously, I just don't see it :( )

    Some of problem 1 has been cut off so I could attach the files

    2. Relevant equations

    How do I figure out if I'm suppose to use a cos or a sin for x or y?

    Attached Files:

  2. jcsd
  3. Jun 4, 2008 #2
    I can't see your images yet, but I'm going to guess the problem is which angle you are using:

    Consider a right angle triangle, with sides x, y and hypotenuse 1 (draw it!). Let's take the angle t to be between the sides x and 1: then cos(t)=adjacent/hypotenuse=x

    But if we take s to be the angle between 1 and y

    Does that answer your question?
  4. Jun 5, 2008 #3


    User Avatar
    Science Advisor
    Homework Helper

    Hi r6mikey! :smile:

    Forget about triangles.

    The component in a direction is always found by multiplying by the cos of the angle between.

    (so you only use sin if it's the "wrong" angle! :biggrin: )
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook