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Starting point 3- First double the trapezium making a parallelogram. From this we can see a smaller parallelogram made from the shaded triangles. Both areas can now be regarded as 2*area. if we split it horizontally, they will be parallelograms but still have the original area. then we can draw lines to make BCE and another point a parallelogram making a 1/2, 1/2 balance. this leave another parallelogram that represents the same thing. Therefor th triangle is 1/2