# How is the triangle exterior angle theorem related to the triangle angle sum theorem?

Asked By: Nino Mazarico | Last Updated: 17th May, 2020
Category: science space and astronomy
4.3/5 (325 Views . 35 Votes)
The exterior angle theorem states that the exterior angle formed when you extend the side of a triangle is equal to the sum of its non-adjacent angles. The theorem tells us that the measure of angle D is equal to the sum of angles A and B.

Keeping this in view, what is the triangle exterior angle theorem?

The exterior angle theorem is Proposition 1.16 in Euclid's Elements, which states that the measure of an exterior angle of a triangle is greater than either of the measures of the remote interior angles. This is a fundamental result in absolute geometry because its proof does not depend upon the parallel postulate.

Secondly, what is the sum of the 3 exterior angles of a triangle? An exterior angle of a triangle is equal to the sum of the opposite interior angles. For more on this see Triangle external angle theorem. If the equivalent angle is taken at each vertex, the exterior angles always add to 360° In fact, this is true for any convex polygon, not just triangles.

Just so, what is the relationship between exterior and interior angle of a triangle?

The angles on the inside are called Interior angles. The sum of the interior angles of a triangle is always 180 degrees. The exterior angle is the angle between any side of a shape, and a line extended from the next side. The sum of an exterior angle and its adjacent interior angle is also 180 degrees.

What is the formula for exterior angle theorem?

Definition & Formula. The exterior angle theorem states that the exterior angle formed when you extend the side of a triangle is equal to the sum of its non-adjacent angles. Remember, our non-adjacent angles are those that don't touch the angle we are working with.

### What does it mean to be congruent?

The adjective congruent fits when two shapes are the same in shape and size. If you lay two congruent triangles on each other, they would match up exactly. Congruent comes from the Latin verb congruere "to come together, correspond with." Figuratively, the word describes something that is similar in character or type.

### How do you find the sum of a triangle?

In a Euclidean space, the sum of measures of these three angles of any triangle is invariably equal to the straight angle, also expressed as 180 °, π radians, two right angles, or a half-turn.

### Is a triangle a polygon?

As you learned in the last lesson, a triangle is the simplest polygon, having three sides and three angles. The sum of the three angles of a triangle is equal to 180 degrees. Triangles are classified by sides and by angles. Move your cursor over the triangles to learn more.

### What is a scalene triangle?

A scalene triangle is a triangle that has three unequal sides, such as those illustrated above. SEE ALSO: Acute Triangle, Equilateral Triangle, Isosceles Triangle, Obtuse Triangle, Triangle. CITE THIS AS: Weisstein, Eric W. "

### Can a triangle have two right angles?

In Euclidian (flat) geometry the sum of all angles, in a triangle, by definition, must be equal to 180 degrees. So, we can't have two right angles in a triangle, only one, because the sum of two other angles must be 90 degrees.

### What does Cpctc stand for?

corresponding parts of congruent triangles are congruent

### What is the triangle sum property?

The Triangle Sum Theorem states that the three interior angles of any triangle add up to 180 degrees.

### What is the exterior angle of an equilateral triangle?

In the case of the equilateral triangle, ??, the exterior angle, plus 60 equals 180. Subtracting 60 from both sides of this equation gives us a value of ?? equal to 120. This means that the exterior angle of an equilateral triangle is equal to 120 degrees. The sum of all the exterior angles is always 360 degrees.

### How do you find the measure of an angle?

Using a Protractor
The best way to measure an angle is to use a protractor. To do this, you'll start by lining up one ray along the 0-degree line on the protractor. Then, line up the vertex with the midpoint of the protractor. Follow the second ray to determine the angle's measurement to the nearest degree.

### What is the third angle theorem?

Third Angle Theorem. If two angles in one triangle are congruent to two angles in another triangle, then the third pair of angles must also congruent. This is called the Third Angle Theorem.

### How do you find the third exterior angle of a triangle?

Because the interior angles of a triangle add to 180°, and angles c+d also add to 180°:
1. The interior angles of a triangle add to 180°:a + b + c = 180°
2. Angles c and d make a straight angle, which is 180°:d + c = 180°
3. So d + c equals a + b + c:d + c = a + b + c.
4. Subtract c from both sides:d = a + b.

### How many exterior angles does a triangle have?

6 exterior angles

### What are the two angles that are non adjacent to the specified exterior angle?

The remote interior angles of a triangle are the two angles that are non-adjacent to the specified exterior angle.

### What is the exterior angle sum theorem?

Polygon Exterior Angle Sum Theorem. If a polygon is convex, then the sum of the measures of the exterior angles, one at each vertex, is 360° . The sum of the measures of the exterior angles is the difference between the sum of measures of the linear pairs and the sum of measures of the interior angles.

### What is the exterior angle Inequality Theorem?

An exterior angle of a triangle is the angle formed between any side of the triangle and an external extension of the adjacent side. The exterior angle inequality theorem states that the measure of any exterior angle of a triangle is greater than both of the non-adjacent interior angles.

### What is the triangle inequality theorem?

The Triangle Inequality Theorem states that the sum of any 2 sides of a triangle must be greater than the measure of the third side.

### Can the exterior angle of a triangle be a straight angle?

AN EXTERIOR ANGLE OF A TRIANGLE CANNOT BE A STRAIGHT LINE BECAUSE A TRIANGLE HAS 180 DEGREES IN ADDING ALL THE THREE ANGLES OF A TRIANGLE.