Question 1133881
Think in terms of base and height.
If the triangle is a cardboard cut-out, lay
one of the sides on the surface of a table.
This is the base. From the vertex above the table
to the surface is the height.
So, I'll translate:
width = base in meters
length = height in meters
The formula for area is:
[ Area ] = (1/2) x [ base ] x [ height ]
[ Area ] = {{{ (1/2)*3.9*4.2 }}}
[ Area ] = {{{ (1/2)*16.38 }}}
[ Area ] = {{{ 8.19 }}} square meters