Area of a triangle using Heron’s formula

[rachelmaddie]

Hi. I need my work checked please.

To calculate the area of a triangle, given its sides,we need to use Heron’s formula.
Heron’s formula is defined by:
Area = (sqrt(p(p - a)(p - b)(p - c))
where p is half the perimeter
p = a + b + c/2

So, we are given the triangle, which sides are:
a = 19 units
b = 14 units
c = 19 units

Find the half perimeter p
p = 19+14+19/2 = 26 units

Now find the area
A = (sqrt(26)(26 - 19)(26 - 14)(26 - 19))
A = (sqrt(26)(7)(12)(7))
A = sqrt(15,288)
A = 123.6 units^2

Solution: The area of the triangle is 123.6 units^2

 

[Dr.Peterson]

Correct answer; but the work is incorrect, and that's what you asked us to check. Why have you not yet learned to use parentheses? Do you not realize that a + b + c/2 is wrong?

Here is what you should have written:

To calculate the area of a triangle, given its sides,we need to use Heron’s formula.
Heron’s formula is defined by:
Area = sqrt((p(p - a)(p - b)(p - c))
where p is half the perimeter
p = (a + b + c)/2

So, we are given the triangle, which sides are:
a = 19 units
b = 14 units
c = 19 units

Find the half perimeter p
p = (19+14+19)/2 = 26 units

Now find the area
A = sqrt((26)(26 - 19)(26 - 14)(26 - 19))
A = sqrt((26)(7)(12)(7))
A = sqrt(15,288)
A = 123.6 units^2

Solution: The area of the triangle is 123.6 units^2

I think you've been told this over and over. When you omit parentheses, you force the reader to take the time to figure out what you mean, which is rude to someone trying to help you.

End of rant.

As an aside, I would never use p to mean the semiperimeter; it is traditional to use s, for obvious reasons.