Can we use the formula a = 1/2 × base × height to calculate the area of triangles that are not right triangles? explain your thinking.

Yes

Step-by-step explanation:

If you are looking for an area of a triangle that is not a right triangle, and it shows the height of that triangle (it should be a dotted straight line), than you can use the formula to get the area.  

So if you know the base and height of a non right triangle, you can use the formula.