Question

In the parallelogram abcd, ab = 21, bc = 13 and bd = 14. Find the length ac. (the diagonals of a parallelogram bisect each other)

Answer 1

A=√s(s-a)(s-b)(s-c)

1/2×a+b+c

1/2(20+13+21)

1/2×54

s=27

√27(27-20)(27-13)(27-21)

s=√15876

s=12