What space Congruent Angles?

Congruent angles are two or much more angles that are identical to one one more (and to themselves). Congruent angles can be acute, obtuse, exterior, or interior angles. That does not matter what kind of edge you have; if the measure of angle one is the same as edge two, they space congruent angles.

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Congruent in geometry means that one figure, even if it is it is (line segment, polygon, angle, or 3D shape), is the same to one more in shape and size. Equivalent angles top top congruent numbers are always congruent.

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Congruent angle Definition

The definition of congruent angles is two or more angles through equal actions in levels or radians. Congruent angles require not confront the same method or be built using the same figures (rays, lines, or line segments). If the 2 angle measurements are equal, the angles space congruent.

If angle B and angle D have the exact same measure, castle are said to have actually congruency.


The easiest means to measure up the variety of degrees in an edge is v a protractor.

Congruent angle Symbol

To talk and also write around or draw angles, us need usual symbols and words to explain them. We have actually three icons mathematicians use:

≅ means one point is congruent come another∠ method an angle∡ is periodically used to suggest a measured angle°, together in 45°, means degreesrad means radians, a method of measuring angle in the metric system


Let"s look at at exactly how we can define these 2 angles:


We can say that ∠O (angle O) and ∠A (angle A) are congruent, and both measure up 55°. We could likewise say that mathematically:

∠O ≅ ∠A∠O = ∠A = 55°

Since both angles measure much less than 90°, they are also acute and are both made utilizing rays. The shorthand description, ∠O and ∠A identifies each angle"s vertex, or point where beam meet.

If you require the measure up in radians, you will certainly write 0.959931 rad.

Reflexive home of Congruence

The Reflexive residential property of Congruence tells united state that any kind of geometric number is congruent to itself. A line segment, angle, polygon, circle, or an additional figure the the provided size and also shape is self-congruent.

Angles have a measurable degree of openness, for this reason they have certain shapes and also sizes. As such every angle is congruent come itself.

Congruent angles Examples

Angles have the right to be oriented in any kind of direction top top a plane and still be congruent. Simply as ∠DOG and also ∠CAT, above, to be congruent however were no “lined up” through each other, therefore too deserve to congruent angles appear in any method on a page.

Here is a drawing that has actually several angles. I m sorry of this angles are congruent?:


All of this angles room congruent.

The direction — the means the 2 angles sit top top the printed web page or display — is unimportant. The method the 2 angles are created is unimportant. If the actions in levels or radians room equal, the angles space congruent.

Drawing Congruent Angles

You can draw congruent angles, or compare possible existing congruent angles, using a drawing compass, a straightedge, and also a pencil.

One of the easiest ways to draw congruent angle is to attract two parallel lines reduced by a transversal. In your drawing, the corresponding angles will be congruent. Girlfriend will have actually multiple bag of angles v congruency.


Another easy means to draw congruent angles is to attract a ideal angle or a ideal triangle. Then, cut that right angle with an angle bisector. If girlfriend bisect the angle exactly, you room left to two congruent acute angles, each measuring 45°.


But what if you have a offered angle and also need to attract an the same (congruent) angle next to it:

Here are the actions for how to draw congruent angles:

Draw a ray to the ideal of your original angle, yet some street away. Produce an endpoint for her ray and also label it. We will speak to ours Point M.Open your drawing compass so the the suggest on the compass have the right to be put on the peak of the present angle, however the pencil does no reach past the attracted line segments or light ray of the currently angle.Without changing the compass, ar the point of the compass ~ above Point M top top your brand-new drawing. Swing an arc indigenous Point M up into the room above your new ray.Move the compass allude to a suggest on one beam of the initial angle, then readjust the illustration compass, therefore the pencil touches the various other point. Below we placed our compass ~ above Point K and reach Point Y through it.Without changing the compass, relocate the compass suggest to the brand-new ray"s point, right here Point U, and swing the arc the intersects v your original arc.Use your straightedge to attach the vertex, here Point M, through the intersection of the 2 arcs. Friend have replicated the present angle.

If you have to compare two angles that space not labeled with their degrees or radians, girlfriend can similarly use a drawing compass to locate points top top both angles and also measure their degree of openness.

If you do not have actually a protractor handy, you have the right to use found objects to gain a sense of one angle"s measurement. The square edge of a sheet of file is 90°. If you fold that edge over for this reason the two sides precisely line up, you have actually a 45° angle.

The place or orientation of two angles has nothing to perform with their congruence. Angles can be congruent while encountering in two different directions.

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Congruent angles Word Problems

Suppose you room told that two angles the two various triangles space congruent. Walk that mean the triangles should be congruent?One angle procedures 91° and also is built of 2 rays. One more angle measures 91° yet is built of 2 line segments. Room the 2 angles congruent?Two angles room each 47°, yet one is do from a line and also ray, the other is make from a heat segment and also a line. Room the two angles congruent?An angle actions 1.8 rad. Is the angle congruent come anything?

Just as any kind of angle is true to chin by being congruent, be true to you yourself by law the work-related first, prior to checking the end the answers!

Two angle of two various triangles have the right to be congruent, but that does not mean you have actually congruent triangles; they might be various sizes, and also their other angles can have different measures.The 2 angles, one measure up 91° and constructed of two rays and also the other, additionally measuring 91° yet constructed of 2 line segments, room congruent. Just the edge matters.Two angles, every measuring 47°, are congruent, no matter just how they space constructed.An edge measuring 1.8 rad is congruent come itself.

What friend learned:

After functioning your way through this lesson and also video, you have actually learned:

Congruent angles DefinitionHow to suggest congruent angles making use of symbolsFind congruent anglesThe reflexive building of congruence