9.(06.04 MC) Calculate the area of triangle CDE with altitude EF, given C(3,-2), D(-1, 2), E(2, 3), and F(0, 1).
4 square units
O 6.2 square units
8 square units
O 8.7 square units

9514 1404 393

  8 square units

Step-by-step explanation:

The base of the triangle, CD, is 4 times the length of the diagonal of a grid square, so is 4√2. The height of the triangle, EF, is 2 times the length of the diagonal of a grid square, so is 2√2. The area is ...

  A = (1/2)bh

  A = (1/2)(4√2)(2√2) = 8 . . . . square units

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In case you don't know it already, the diagonal of a unit square can be found from the Pythagorean theorem:

  d² = 1² + 1²

  d = √2