Find the area of a triangle whose two sides are 10 inches and 18 inches long, and has a perimeter of 42 inches.

Answer 1

the 3rd side is 42 - 10 -18 = 14

half the perimeter = 21

Use heron's formula to find the area = sqr(21)(3)(7)(11) = 21sqr11 square inches = about 69.3 sq. in.

heron's formula uses half the perimeter as p

then Area = sqr[p(p-10)(p-18)(p-14)

subtract each side from half the perimeter, multiply them all together and times p=21,

then take the square root.