# Diagonals at right angle

In the trapezoid ABCD, this is given:

AB=12cm

CD=4cm

And diagonals crossed under a right angle. What is the area of this trapezoid ABCD?

AB=12cm

CD=4cm

And diagonals crossed under a right angle. What is the area of this trapezoid ABCD?

## Correct answer:

**Showing 1 comment:**

**Math student**

I don't think the solution is correct. The height is the radius if and only if the trapezoid is symmetrical. But it doesn't have to be. In fact, take a line segment of length 12 and start a 20 degree angle from one side and 70 from the other (for the diagonals). Intersect them and keep going until there is 4 long parallel line. Then increase the 20 degree angle - the height will increase and the area too.

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### You need to know the following knowledge to solve this word math problem:

**geometry**- Thales' theorem
- similarity of triangles
**planimetrics**- right triangle
- area of a shape
- triangle
- trapezoid
- diagonal
**basic functions**- functions

### Units of physical quantities:

### Grade of the word problem:

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