you know the area of a triangle is
\[\frac{ 1 }{ 2 } b h\]
|dw:1370581830579:dw|
as you can see...you have 2 right triangles
the hypotenuse is 6...and the bottom side is 6/2 = 3
so now you have 1 side...the hypotenuse...find the other side *which will be your height* using the Pythagorean theorem
3² + b² = 6²

no ..what you get from
b = √(6² - 3²)
will be your height
Then you plug THAT into that other equation along with the base length (6)
\[\frac{ 1 }{ 2 } (6) (height)\]

well lets see 36 - 9 = 27
√ 27 = 5.19615242270
that is your height
\[\frac{ 1 }{ 2 } (6) (5.19615242270)\]
and that comes out to 15.59 would be the area