Find the area of the triangle whose vertices are (–8, 4), (–6, 6) and (–3, 9).
Find the area of the triangle whose vertices are (–8, 4), (–6, 6) and (–3, 9).

Solution:

The provided vertices are:

$({{x}_{1}},\text{ }{{y}_{1}})\text{ }=\text{ }\left( -8,\text{ }4 \right)$

$({{x}_{2}},\text{ }{{y}_{2}})\text{ }=\text{ }\left( -6,\text{ }6 \right)$

$({{x}_{3}},\text{ }{{y}_{3}})\text{ }=\text{ }\left( -3,\text{ }9 \right)$

The area of triangle $=\text{ }\left( 1/{{}_{2}} \right)\text{ }({{x}_{1}}({{y}_{2}}-{{y}_{3}})\text{ }+\text{ }{{x}_{2}}({{y}_{3}}-{{y}_{1}})\text{ }+\text{ }{{x}_{3}}({{y}_{1}}-{{y}_{2}}))$

$=\text{ }\left( {\scriptscriptstyle 1\!/\!{ }_2} \right)\text{ }\left( -8\left( 6\text{ }\text{ }9 \right)\text{ }+\text{ }-6\left( 9\text{ }\text{ }4 \right)\text{ }+\text{ }-3\left( 4\text{ }\text{ }6 \right) \right)$

$=\text{ }\left( {\scriptscriptstyle 1\!/\!{ }_2} \right)\text{ }\left( -8\left( -3 \right)\text{ }+\text{ }-6\left( 5 \right)\text{ }+\text{ }-3\left( -2 \right) \right)$

$=\text{ }\left( {\scriptscriptstyle 1\!/\!{ }_2} \right)\text{ }\left( 24\text{ }\text{ }30\text{ }+\text{ }6 \right)$

$=\text{ }\left( {\scriptscriptstyle 1\!/\!{ }_2} \right)\text{ }\left( 30\text{ }\text{ }30 \right)$

$=\text{ }0\text{ }units$.