For a triangle with sides $a,b,c$ and semiperimeter $s$, Heron's formula for its area $\Delta$ is 
A$\Delta=\dfrac{abc}{2}$
B$\Delta=\sqrt{s(s-a)(s-b)(s-c)}$
C$\Delta=\dfrac{a+b+c}{2}$
D$\Delta=\dfrac{ab+bc+ca}{4}$
Answer & Solution
Correct answer: B. $\Delta=\sqrt{s(s-a)(s-b)(s-c)}$
Heron's formula states that if $s=\frac{a+b+c}{2}$, then the area is $\Delta=\sqrt{s(s-a)(s-b)(s-c)}$. Option C is just the semiperimeter, not the area.
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