Given the points A(0,0), B(4,3) and C(2,9), what is the measure of <ABC?

Answer 1

figure side lengths, then use the law of cosines.

AB^2 = 25
BC^2 = 40
AC^2 = 85

AC^2 = AB^2 + BC^2 - 2*AB*BC*cosABC
85 = 25+40-2√1000 * cosABC
<ABC =~ 109°

Answer 2

Thanks Steve