## Winter Diet 2002 non calc Question help

### Ry4n

Posted 18 May 2004 - 07:32 PM

Could anyone give me some help with Q1.b

Q1. Find the equation of the straight line through the points A(-1,5) B(3,1)

it works out to be y+x=4

b. Find the size of the angle which Ab makes with the positive direction of the x- axis

m = tan(X)
m = -1

How would I work it out?

### xpurple_starsx

Posted 18 May 2004 - 07:42 PM

At 1 you should know that tan is 45 degrees.
Since you want to know when m=-1 you should do 180-45 (since the x-axis is a straight line with an angle of 180) which gives you an angle of 135 degrees as the answer.

### sparky

Posted 18 May 2004 - 07:42 PM

You need to use your exact values

Tan is 1 when the angle is 45 degrees.

Tan is negative in 2nd and 3rd,

so m = tan -1 => 2nd QUAD 180 - 45 = 135 degrees.

(it now appears someone beat me to this post! )

### Ry4n

Posted 18 May 2004 - 07:44 PM

lol, didn't think it was so simple , thanks

### AndyW

Posted 18 May 2004 - 09:48 PM

I came across this question the other day and thought it seemed ambiguous. Couldn't you say that it was 135 degrees? It depends how you measure it. Is there some standard convention?

### George

Posted 18 May 2004 - 10:32 PM

I think "the positive direction of the x- axis" implies it is measured anti-clockwise from the x-axis.

### Fraizer

Posted 18 May 2006 - 07:04 PM

This is confusing,,

its either in the second or third quad. right?

How do u know which 1? coz Im getting:

180 - 45

AND

180 + 45

which are two totally different answers
:S