As shown in the figure, in the triangle ABC, ab = BC, ad is the middle line on BC, extend BC to point E, make CE = BC, prove: AE = 2ad

As shown in the figure, in the triangle ABC, ab = BC, ad is the middle line on BC, extend BC to point E, make CE = BC, prove: AE = 2ad

Let ∠ AEB = ∠ 1, ∠ ACB = ∠ 2, ∵ AB = BC, ad is the middle line on BC, ∵ AEB = ∠ 1 = ∠ EAB, ∵ ACB = ∠ 2 = ∠ CBA, and then set ∠ bad = ∠ 4, ∵ DAC = ∠ 3, ∵ ADB = ∠ 5, ∵ ADC = ∠ 6, ∵ 5 + ∠ 6 = 180 °, 2 ∠ 2 + ∠ 6 = 180 ° + ∠ 4, ∵ 6 = 2 ∠ 1 + ∠ 2 - ∠ 3,