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Find the coordinates of the vertices of the triangle $ABC$ formed by the intersection of the lines $x + y = 0$, $x = 0$ and $y = x - 1$. Hence, find the area of the triangle.

I tried to sketch a graph but since the $y$ coordinate could be anywhere, I am having trouble working it out.

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    You don't *have* to sketch a graph (though in this case it certainly makes it easier to solve the rest of the question). You can take two of the lines and solve the equations simultaneously to find the $x$ and $y$ coordinates of a vertex of the triangle; repeat for the other two possible pairs of lines.2012-08-16

3 Answers 3