What is the area of triangle ABC?

see the attached figure to better understand the problem
we know that
the area of the triangle ABC is equal to the area of the triangle 1
The area of the triangle 1,2,3 and 4 is the area of a rectangle
The area of the rectangle is equal to
[tex]A=3*5=15\ units^{2}[/tex]
Find the area of the triangle 2
[tex]A2=\frac{1}{2}*(2*4)=4\ units^{2}[/tex]
Find the area of the triangle 3
[tex]A2=\frac{1}{2}*(1*5)=\frac{5}{2}\ units^{2}[/tex]
Find the area of the triangle 4
[tex]A2=\frac{1}{2}*(3*1)=\frac{3}{2}\ units^{2}[/tex]
Find the area of the triangle ABC
[tex]A1=15\ units^{2}-(4\ units^{2}+\frac{5}{2}\ units^{2}+\frac{3}{2}\ units^{2})\\ \\A1=15\ units^{2}-(8\ units^{2})\\ \\ A1=7\ units^{2}[/tex]
therefore
the answer is
the area of the triangle ABC is equal to
[tex]7\ units^{2}[/tex]
7 square units
Let us find out the area of triangle ABC using an alternative method.
We divide the triangle ABC into three triangles, which are:
We prepare the base and height of each triangle.
ΔAOC
ΔAOB
ΔBOC
To recall the base and height of an obtuse triangle, look at the attached picture.
The formula of area of triangle is [tex]\boxed{ \ Area = \frac{1}{2} \times base \times height \ }[/tex]
Let us calculate the area of each triangle.
The area of triangle AOC = [tex]\boxed{ \ \frac{1}{2} \times 2 \times 4 = 4 \ square \ units \ }[/tex]
The area of triangle AOB = [tex]\boxed{ \ \frac{1}{2} \times 2 \times 1 = 1 \ square \ units \ }[/tex]
The area of triangle BOC = [tex]\boxed{ \ \frac{1}{2} \times 4 \times 1 = 2 \ square \ units \ }[/tex]
And now, let us find out the area of triangle ABC.
The area of ΔABC = the area of ΔAOC + the area of ΔAOB + the area of ΔBOC
The area of ΔABC = 4 + 1 + 2
The area of ΔABC = 7
Thus, the area of triangle ABC is 7 square units.
Keywords: what, the area of triangle ABC, right, obtuse, base, height, formula, alternative method