In a convex quadrilateral ABCD, the length of the diagonal AC is equal to the length of the side AD. Prove that ВС
| September 16, 2021 | education

Since ACD in triangle AC = AD, ACD triangle is isosceles and the angles at the base of the triangle are: <ACD = <ADC.
When solving the problem, one of the basic rules in a triangle is used: The large side in the triangle is opposite the larger angle.
Now consider the angles in the triangle BCD. The angle against the side BD – <BCD = <ACD + <BCA, And the angle against the side BC <BDC = <BCD – <BCA. That is, the angle against the side BC is less than the angle against the side BD in one triangle BDC . Hence, BC <BD.



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