Added by Bill T****** on November 09, 2001 at 06:59:07:
FORMULA 1:
a = 1/2bh (1/2 x b x h)
Where b = length of base, & h = height from base.
FORMULA 2:
a = 1/2ab.sinC (1/2 x a x b x sinC)
Where a = side length a, b = side length b, & sinC = sin of angle C (angle opposite to side c).
FORMULA 3:
a = SQRT(s(s-a)(s-b)(s-c)),
Where s = (a + b + c)/2 (or perimeter/2), a = side a, b = side b, & c = side c.