Question

Tell whether the following set is an empty set or not.

A = {A quadrilateral having 3 obtuse angles}

Answer 1

It is not an empty set

Explanation:

A quadrilateral with 3 obtuse angles is possible.

A obtuse angle has a measure of more than 90 degrees and less than 180 degrees.

Let’s say three angles are measuring 91 degrees in a quadrilateral.

91 + 91 + 91 + x = 360

x = 87

The measure of the fourth angle is 87 degrees which is less than 360 degrees and is a positive integer, so it is possible.

Answer 2

It is not an empty set

Explanation:

Obtuse angles are angles greater than 90 and less than 180.

There are quadrilaterals having 3 obtuse angles and they are possible.

If we imagine 3 obtuse angles of 91 degrees (obtuse angle), the 4th angle will be

360-91-91-91

=> 87 degrees

So, This quadrilateral can be constructed!

And also with 92, 93, 94 and so on!

So, Set A is not an empty set!