Question

find the area of triangle whose vertices are (1,-2) (-3,4) (5, -6)

Answer 1

(1,-2)=(x1,y1)
(-3,4)=(x2,y2)
(5,-6)=(x3,y3)

$\frac{1}{2} |x1(y2 - y3) +x2(y3 - y1) \\ + x3(y2 - y1)|$
1/2|1(4+6)-3(-6+2)+5(4+2)|

1/2[10+12+30]
1/2(52)
26 sq units