Question

find the acute angel formed by the two lines.
y=1/3x+7 and y=-1/2x-8
please help..

Answer 1

Ah ha. Yah. You can find the angles each of these makes with the x axis. Then, you use this information to know what angles they will have between them. One pair will be the obtuse, the other the acute.

Answer 2

im confused..?

Answer 3

OK. Well, slope is rise over run, right? Well, what is tangent?

Answer 4

tan is rise over run?

Answer 5

Yes, it is sine over cosine, so Y over X, which is Rise over Run. That means you can use Tan to find both the angles of each line with respect to the X axis. Then it is math to get them with repect to each other.

Answer 6

do i plug that into my calculator?

Answer 7

Well, they probably want exact values, so you may need to find out what it is in terms of radian and pi.

Answer 8

I am going to look and see if someone has an equation to solve it faster. But here is what I mean so far in a graphical way.

Answer 9

Take a look at : http://www.transtutors.com/math-homework-help/straight-line/angle-between-two-lines.aspx and see if that makes sense. If not, what part so we can go from there.

Answer 10

i just tried and te acute angel they make is 98 degrees. i think i did it wrong..?

Answer 11

when i do tan(1/2) i get 55 degrees and tan(1/3) is 35 degrres when i add them together i get 90 degrees??

Answer 12

Well, that is not the best description. I found another, that is clearer. It is the same thing, but better written. I tested it, and confirmed grapically. http://www.tpub.com/math2/5.htm I'll put in some of the math in another post so you can see what I did.

Answer 13

The key is the: \[\tan \theta = \frac{ m_2-m_1 }{1+ m_2m_1}\] Lets take your slops as m1=-1/2, and m2=1/3.

Answer 14

Then: \[\tan \theta = \frac{ \frac{1}{3}-(-\frac{1}{2}) }{1+ \frac{1}{3}(-\frac{1}{2}) }\]

Answer 15

Now, can you see how that simplifies? It becomes a reaaaaaaaaly easy number.

Answer 16

0/1? or just 0? or 1?

Answer 17

is it 1?

Answer 18

do i do inverse tan(1) ?

Answer 19

@e.mccormick

Answer 20

Yah, absolutly! You are there.

Answer 21

The arctan(1)

Answer 22

so the answer is 78 degrees?

Answer 23

Your calculator is in radians mode.

Answer 24

no sorry 45 degrees?

Answer 25

Yep! Once I found a better copy of the formula, it was easy. Sorry about linking the poorly done one. It was jsut confusing.

Answer 26

its okay thank you so so much! you wanna help me with another problem? im gonna post it.

Answer 27

More trig? Sure. I need some trig brushup.

Answer 28

yep;)

Answer 29

Yah, best way to remember these thing is to work them through and talk about them. So it helps me as much as it helps you.