Intermediate Geometry : How to find the area of an acute / obtuse isosceles triangle

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #21 : Triangles

An isosceles triangle is placed in a circle as shown by the figure below.

1

If the diameter of the circle is , find the area of the shaded region.

Possible Answers:

Correct answer:

Explanation:

2

From the given image, you should notice that the base of the triangle is also the diameter of the circle. In addition, the height of the triangle is also the radius of the circle.

Thus, we can find the area of the triangle.

Next, recall how to find the area of a circle.

To find the area of the shaded region, subtract the two areas.

Make sure to round to  places after the decimal.

Example Question #22 : Triangles

An isosceles triangle is placed in a circle as shown by the figure below.

1

If the diameter of the circle is , find the area of the shaded region.

Possible Answers:

Correct answer:

Explanation:

2

From the given image, you should notice that the base of the triangle is also the diameter of the circle. In addition, the height of the triangle is also the radius of the circle.

Thus, we can find the area of the triangle.

Next, recall how to find the area of a circle.

To find the area of the shaded region, subtract the two areas.

Make sure to round to  places after the decimal.

Example Question #21 : Acute / Obtuse Isosceles Triangles

An isosceles triangle is placed in a circle as shown by the figure below.

1

If the diameter of the circle is , find the area of the shaded region.

Possible Answers:

Correct answer:

Explanation:

2

From the given image, you should notice that the base of the triangle is also the diameter of the circle. In addition, the height of the triangle is also the radius of the circle.

Thus, we can find the area of the triangle.

Next, recall how to find the area of a circle.

To find the area of the shaded region, subtract the two areas.

Make sure to round to  places after the decimal.

Example Question #461 : Intermediate Geometry

A triangle is placed in a parallelogram so that they share a base.

9

If the height of the triangle is half the height of the parallelogram, find the area of the shaded region.

Possible Answers:

Correct answer:

Explanation:

13

In order to find the area of the shaded region, we will need to find the areas of the triangle and of the parallelogram.

First, recall how to find the area of a parallelogram.

Next, recall how to find the area of a triangle.

Now, find the height of the triangle.

Plug this value in to find the area of the triangle.

Subtract the two areas to find the area of the shaded region.

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