Question

How many triangles can be drawn with one 90o ​angle, a 70° angle, and an included side measuring 3​ inches? Explain. Select the correct choice below​ and, if​ necessary, fill in the answer box to complete your choice.

Answer 1

2

Explanation:

This is because any of the sides can be the one measuring 3 inches. Since it is a triangle, the sum of angles is 180. Let the third angle be x.

So, x + 90° + 70° = 180°

x + 160° = 180°

x = 180° - 160°

x = 20°

So, the third angle is 20°.

If the included side is a side other than the hypotenuse side, we can find it by applying the sine rule.

The included side can be either side other than the hypotenuse.

Also, either of the third angle in each triangle can be 20°

So, we have two sides and two triangles.

If the included side is the hypotenuse side, we use Pythagoras' theorem to find the length of the other two sides (and they must be equal)since the angle between the two sides is a right-angle, that is, 90°.

Since the other two angles are not equal, we cannot have a triangle with two equal sides and an hypotenuse. That is, we cannot have an isosceles triangle. So, no third triangle.

So, the total number of triangles that can be drawn with one 90° angle, a 70° angle and an included side measuring 3 inches is 2.