2090

The blue shape is an isosceles trapezoid. Prove the red circles are tangent to each other.

2089

The blue shapes are isosceles trapezoids. Prove the red line segments are congruent.

1995

Given an isosceles trapezoid. Prove $r = \frac{1}{2}\left( s + t + \sqrt{s^2+t^2} \right)$.

1968

The blue shape is an isosceles trapezoid. Prove the red line segments are congruent.

1369

One base of the blue trapezoid is three times the other base. Prove the red lines are perpendicular.

1336

Prove the rhombus and isosceles trapezoid have the same area iff the their acute angles are congruent.

944

Prove the red line segments are congruent.

569

Prove the red line segments are congruent.

330

Prove the blue line is perpendicular to one of the legs of the isosceles trapezoid.

304

Prove the red line is perpendicular to the bases of the isosceles trapezoid.

208

Given an isosceles trapezoid. Prove $$A=\frac{a+b}{2},\qquad G=\sqrt{ab},\qquad H=\left(\frac{\frac1a+\frac1b}{2}\right)^{-1}$$ and $$\min\{a,b\}\le H\le G\le A\le\max\{a,b\}$$

107

The centers of the circles are midpoints of a side and a diagonal of an isosceles trapezoid. Prove the red points are collinear.