Really dont understand this question, how do I relate tanA and tanB with the equations?The lines l1 and l2, with equations y=2x and 3y=x−1 respectively, are drawn on the same set of axes. Given that the scales are the same on both axes and that the angles that l1 and l2 make with the positive x-axis are A and B respectively,
(a) write down the value of tan A and the value of tan B;
(b) without using your calculator, work out the acute angle between l1 and l2.
Hi Tweety,
the slope of a line can be represented by placing a right-angled
triangle against it.
If the line has a positive slope, place the triangle under it,
so that the tangent of the lower left corner angle is opp/adj.
This is the exact same way to calculate the line slope,
using the differences between co-ordinates.
If the line has a negative slope, use the negative of the triangle's
tangent. So, a negative tangent means the slope of a negative-going line.
tan(angle) = line slope.