Question

Find the area of a triangle formed by points(8,-5),(-2,-7),(5,1)

Answer 1

Area of a triangle
= |x1(y2-y3) +x2(y3-y1) +x3(y1-y2)| ÷ 2

= 8[(-7)-1] +(-2)[5-(-5)] +5[(-5)-(-7)] ÷ 2
= { 8×(-8) + (-2)×0 + 5×2 } ÷ 2
= (-64+10)/2
= |-54|/2
Area = 27 unit square
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Answer 2

Area of a triangle
= [x1(y2-y3) +x2(y3-y1) +x3(y1-y2)] / 2

= 8[(-7)-1] +(-2)[5-(-5)] +5[(-5)-(-7)] / 2
= [ 8×(-8) + (-2)×0 + 5×2 ] ÷ 2
= (-64+10)/2
= |-54|/2
Area of the triangle  = 27 square units.