• Support PF! Buy your school textbooks, materials and every day products Here!

General question

  • Thread starter Cursed
  • Start date
39
0
This isn't a problem, but I need help understanding this so I can do problems.

http://img255.imageshack.us/img255/3479/xythingat6.png [Broken]

So let's say...
1. This is part of the motion of a projectile
2. You're trying to find x and y

There are trig. identities that will give you x and y.

Example:
x = sin(36)*10
y = cos(36)*10

My question is... Which trig. identity/function do you use to solve for x, and why do you use that identity? Also explain the same thing for y. Please and thank you.
 
Last edited by a moderator:

Answers and Replies

mgb_phys
Science Advisor
Homework Helper
7,744
11
It's the basic defn of sin and cos.

Sin is the ratio of the opposite side over the hypotonuse
Cos is the ratio of the adjacent side over the hypotonuse

If you draw a line down to the X axis from the end of the slope (opposite the 36deg) you have a triangle.
The hypotonuse is 10units, the adjacent side is the distance in x and the opposite side (the exta line you just drew) the opposite side.
 
Dick
Science Advisor
Homework Helper
26,258
618
And following mgb_phys' instructions you should find x=cos(36)*10 and y=sin(36)*10, the opposite of what you wrote.
 
Last edited:
1,341
3
[tex]sin x = \frac{opposite}{hypotenuse} [/tex]

[tex]cos x = \frac{adjacent}{hypotenuse} [/tex]

So applying that to your problem:

[tex]sin(36) = \frac{y}{10}[/tex]

[tex]cos(36) = \frac{x}{10}[/tex]

From there it's really straight forward for solving for x and y.
 

Related Threads for: General question

  • Last Post
Replies
4
Views
567
  • Last Post
Replies
6
Views
3K
  • Last Post
Replies
0
Views
1K
  • Last Post
Replies
3
Views
1K
Replies
5
Views
2K
Replies
1
Views
1K
Replies
4
Views
1K
Replies
3
Views
2K
Top