The lines 3x-7y=-15 and 4x+2y=9 and the x-axis intersect to form a triangle. How many degrees are in the angle of the triangle where the two lines intersect?

Question

campbell_st · Answer

well is basically the tan formula for the difference 

start my finding the slope of each line

line 1

$$\frac{3}{7}x + \frac{15}{7} = y$$

slope m = 3/7

line 2

$$y = -2x + \frac{9}{2}$$

slope = -2

then you need 

$$\tan (\theta) = \frac{m_{1} - m_{2}}{1 + m_{1}m_{2}}$$

hope it helps

campbell_st · Answer

you should also graph the lines... so you can make sense of the answer... as to whether the angle is acute of obtuse