David W. answered 09/15/16
Tutor
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(90)
Experienced Prof
First, plot the triangle. Label the points A(1,2). B(7,4) and C(3,6).
Then, be sure that it is a right triangle as stated (note: have you never been "tricked?"). The line segments A(1,2)C(3,6) [with slope 2] and C(3,6)B(7,4) [with slope (-1/2) are perpendicular (inverse reciprocal slope). O.K., it is a right triangle.
The area of the triangle is (1/2)bh.
h = distance CB is 2√5 [distance formula: d = ( (y2-y1)2 + (x2-x1)2 ) ]
b = distance AC is 2√5 [distance formula again]
A = (1/2)bh
A = (1/2)(2√5)(2√5)
A = (1/2)(4)(5)
A = 10 square units ("to the nearest hundredth", this is 10.0]