Question 985866
The obtuse angle b/w the line y=-2 and y=x+2
<pre>

The slope of y=-2 is m=0 because in slope-intercept form it's y = 0x-2, and
the coefficient of x is 0.

The slope of y=x+1 is m=1 because the coefficient of x is 1


{{{tan(theta)}}}{{{""=""}}}{{{"" +- abs(((m[1]-m[2])/(1+m[1]m[2]))) }}}, taken positive when we want the acute angle, 
and negative when we want the obtuse angle. 

{{{tan(theta)}}}{{{""=""}}}{{{"" +- ((0-1)/(1+0*1)) }}}
{{{tan(theta)}}}{{{""=""}}}{{{"" +- 1 }}}

We take the negative value since we want the obtuse angle:

{{{theta = "135°"}}}

{{{drawing(400,400,-6,2,-5,3, graph(400,400,-6,2,-5,3),
line(-10,-2,10,-2), line(10,12,-10,-8),locate(-4.8,-1.3,theta="135°"),
red(arc(-4,-2,2.4,-2.4,45,180))  )}}} 


Edwin</pre>