Area = Half of base ( divided by 2) x Perpendicular height.
If you had a triangle and one of the sides was 10 cm, the other side was 8 cm and the other side was 6cm. Then the right angle was joint between the 8cm and 6 cm. The area would be b x h divided by 2. You would do 6 x 8 = 48, then 48 divided by 2 = 24 cm cubed. That is the same as doing half of 8 = 4. 4 x 6 = 24 cm squared.