There is an isosceles concyclic trapezium ABCD. AB II CD and AB > C...
In ΔAEO,
AE = AB/2 = 5 cm
EO = 5√3 cm
AO = 10 cm
Hence, option 1.
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There is an isosceles concyclic trapezium ABCD. AB II CD and AB > C...
Understanding the Problem
We have an isosceles trapezium ABCD, where AB is parallel to CD, and the lengths are given as follows:
- AB = 10 cm
- The perpendicular distance from the center of the circle to AB = 5√3 cm
Since ABCD is concyclic, the trapezium is inscribed in a circle.
Circle Properties
To find the radius (R) of the circle, we can apply the following properties:
- The trapezium is symmetric because it is isosceles.
- The distance from the center of the circle to the bases (AB and CD) will help us find the radius.
Calculating the Radius
1. Identify the distances:
- Let O be the center of the circle.
- The distance from O to AB is 5√3 cm.
- Let h be the distance from O to CD (the shorter base).
2. Use the trapezium's properties:
- In an isosceles trapezium, the distance from the center of the circle to the bases can be expressed using the radius.
- The height (h) from the center to the lower base CD can be derived from the trapezium's symmetry.
3. Applying the Pythagorean Theorem:
- The radius R is the hypotenuse in the right triangle formed by the height and half the difference of the bases:
\[
R^2 = (5√3)^2 + \left(\frac{AB - CD}{2}\right)^2
\]
- Here, since AB > CD, let's denote CD as x (unknown).
- The height from the center to CD can be calculated as \(R - 5√3\).
4. Finding the radius:
- Since the bases are parallel and the geometry is symmetric, we can deduce that:
\[
R = 10 \text{ cm}
\]
Thus, the radius of the circle is 10 cm.
Conclusion
The correct answer is option A: 10 cm. This radius satisfies the conditions of the isosceles trapezium being inscribed in a circle.
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