What is the formula of triangle area?

Answer 1

There are different formulae, depending on what information you have:

If base, b, and vertical height, h, then 0.5*b*h

If two sides: a and b and included angle C, then 0.5*a*b*sin(C)

If three sides: a, b and c then sqrt[s*(s-a)*(s-b)*(s-c)] where s = 0.5*(a+b+c)

there are many other formulae.

Answer 2

base times height, then divide by two because a triangle is half of a square or rectangle right?