Big Ideas Math Geometry, 2014
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Big Ideas Math Geometry, 2014 View details
1. Angles of Triangles
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Exercise 46 Page 238

Practice makes perfect
a Let's look at the given triangle.
The triangle seems to have three equal sides. If it does, it is an equilateral triangle. Note that we cannot be sure the sides are equal without making measurements.

Checking Our Answer

Checking Our Answer
Let's check our answer using a ruler! To do so, we measure all the sides.
As we can see, all the sides are the same length, which confirms that the triangle is equilateral.
b Take a look at the given triangle.
Looking at the triangle, we are going to assume that the two longer sides have equal lengths. If they do, this is an isosceles triangle. It is also clear that all the angles are acute. This makes the triangle an acute isosceles triangle. Note that we cannot be sure that this is right without making measurements.

Checking Our Answer

Checking Our Answer
Let's check our answer using a ruler! To do so, we measure the two sides we assumed are equal.
As we can see, the two sides are indeed the same length. It is also clear that the third side is not the same length, which confirms that the triangle is isosceles.
c Let's look at the given diagram.
Examining the triangle, we can assume that none of its sides have equal lengths, which would make this a scalene triangle. Additionally, we can see that one of the angles is greater than 90^(∘), which would make the triangle a scalene obtuse triangle.

Checking Our Answer

Checking Our Answer
Let's check our answer using a ruler! To do so, we measure all the sides.
As we can see, all the sides have different lengths. Therefore, the triangle is indeed an obtuse triangle.
d Let's look at the last triangle.
Looking at the triangle, we assume that the angle in the left corner of the triangle is 90^(∘). If that indeed is the case, the triangle is a right triangle. Since none of the side lengths appear to have the same measure, we can call the triangle scalene. Thus we have a scalene right triangle.

Checking Our Answer

Checking Our Answer

Let's check our answer using a ruler and a compass! To do so, we first measure the angle that we assumed was a right angle.

The angle is indeed a right angle. Now let's confirm the triangle is scalene by measuring all the sides.
As we can see, all the sides have different lengths. Therefore the triangle is indeed a scalene right triangle.