math people HELP!...quick trig question...

[jonnyjack]

given y=2x, how do i find the angle it makes with the x-axis? TIA

 

[nightowl]

To find this you find the ratio of 2 of the sides of the triangle that y=2x makes. Once you have the ratio of 2 side then take the inverse trig function of that ratio.
/|
y=2x / |y
/ |
/----
x
exe: tan^-1 (y/x)

It does not matter what sides you use just make sure you use the correct trig function.
(it may not be called the inverse trig function but the button on your calc will be the trig function to the negative one power.)

Edit: click on edit to see the diagram, the formatting was lost when I posted it

 

[Scrapster]

Well, you can graph it or plug in an x and solve for y or vis versa.

Sounds like you wanna know what angle the hypotenuse makes. So you can solve for x and y. If you take the angle to be at the base of the origin. You know your opposite side (y) and adjacent side (x).

To find the angle you solve for theta:

tan(theta) = opposite/adjacent
(once you know what the right side is, take the inverse tangent of that to find theta). And make sure you're in the right calculuator mode if you're solving in degrees or radians.

 

[jonnyjack]

OK...i got it...thanks...

the answer i got is theta=63.4°

is that correct?

 

[Scrapster]

Yeap, I get the same thing.

 

[jeffnoblacks]

That is the solution I come to.