Area of an arrowhead formula

As seen in the figure, the area of the square is 36 in^2. There are 2 right triangles with base 6 and height 3 (x is given as midpoint). Area of one triangle is 1/2 * 6 * 3=9 in^2 There is one isosocles triangle at the bottom with base 6 and height 3 (y is given as the center). The area is 1/2 * 6 * 3= 9 in^2 
We then subtract the triangle areas from the square. 36-3(9)=36-27=9 in^2 
Or draw a line from x to y. There are two triangles with height 3 and base 3. 1/2 * 3 * 3 * 2=9 in^2 

You're doing something i dont know how to do but search up on google slope calculator maybe that will get you there