Question

Calculate the area of triangle ABC with altitude CD, given A(6,-2) B(1,3) C(5,5) D(2,2)

Answer 1

The area will be half the product of the lengths of AB and CD.

|AB| = √((6-1)² +(-2-3)²) = 5√2
|CD| = √((5-2)² +(5-2)²) = 3√2

Area = (1/2)*(5√2)*(3√2) = (1/2)*(15*2) = 15

The appropriate choice is ...
  D: 15 square units