Question

Find the inclination, Ø, of the line with given slope $m = \frac{ - 21}{5}$

Answer 1

we know that

the slope is equal to the the tangent of the angle

so

m=-21/5

tan(∅)=-21/5

using a calculator

∅=-76.6 degrees

but the angle lies on the second quadrant

so

∅=180-76.6

∅=103 4 degrees

the answer is the option D

because the angle lies in the second Quadrantt