Lesson 4.4 are there congruence shortcuts




















What is the minimum number of parts that you would need to duplicate in order to create congruent triangles? How about two parts? Goal is to make two different triangles…show that they are not congruent! Stirling Page 1 of 5. A T y x SS Congruence? Three Parts Part 1: at least two pairs of sides equal.

If the triangles have the same size and shape, they are congruent. If you can create two different triangles from the given parts, then that method does not guarantee congruence. YES If the three sides of one triangle are congruent to the three sides of another triangle, then the triangles are congruent.

YES If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the triangles are congruent. NO If two sides and the non-included angle of one triangle are congruent to two sides and the non-included angle of another triangle, then the triangles are NOT necessarily congruent.

Three Parts Part 2: at least two pairs of angles equal. YES If two angles and the included side of one triangle are congruent to two angles and the included side of another triangle, then the triangles are congruent. YES If two angles and a non-included side of one triangle are congruent to the corresponding angles and side of another triangle, then the triangles are congruent.

Hint: Find the measure of the third angle first. Then do ASA. Reuleaux triangle wikipedia , lookup. History of geometry wikipedia , lookup. History of trigonometry wikipedia , lookup. Pythagorean theorem wikipedia , lookup. Integer triangle wikipedia , lookup. Euclidean geometry wikipedia , lookup. Name all angles congruent to CGI in the figure at right.

Explain why JBH is isosceles. In Exercises 11 and 12, find the missing coordinates. In Exercises , arrange the unknown measures in order from greatestto least.

Whats wrong with this picture? Explain why PQS is isosceles. Explain why the sum of the three altitudes of a triangle is always lessthan its perimeter. Name Period Date In Exercises 13, use a compass and a straightedge or patty paper and astraightedge to construct a triangle with the given parts.

In Exercises 46, name the conjecture that leads to each congruence. M is the midpoint of AB 8. Find the coordinates ofD and G. Name Period Date 1. PS is the angle bisector 7. EFGH is a parallelogram. GQ EQ. Give the shorthand name for each of the four trianglecongruence conjectures. In Exercises 2 and 3, use the figures at right to explain why each congruence is true. W Y For Exercises 8 and 9, copy the figures onto your paper and mark themwith the given information.

Draw at least one more triangle with two congruent angles,and compare the side lengths. Your findings should provide evidencethat the converse of the Isosceles Triangle Conjecture is true. Converse of the Isosceles Triangle Conjecture If a triangle has twocongruent angles, then it is an isosceles triangle. Because A and B are the base angles of anisosceles triangle, they are congruent. So, mA 12 So,mECD By the Triangle Sum Conjecture, 42 96 mD Solving for mD gives mD Therefore, the legs are congruent, so EC ED 3 cm.

Look for a relationship between the measure of the exterior angle of atriangle and the measures of the corresponding remote interior angles. If you are given three segments, will you always be able to form a trianglewith those segments as sides?

In the following investigation, you will explorethis question. In Step 1 of the investigation, you are given two sets ofthree segments to use as side lengths of triangles. Considerthe first set of segments.

To construct the other two sides of the triangle, swing anarc of length AC centered at point C and an arc of lengthAT centered at point T. Point A is where the two arcs intersect. Now try to use the second set of segments to construct FSH. Are you able to doit? Why or why not? You should have found that the arcs that you made using the lengths of two ofthe sides did not intersect, so it was not possible to construct FSH. In general,for three segments to form a triangle, the sum of the lengths of any two segmentsmust be greater than the length of the third segment.

Here are two ways tovisualize this. Imagine two of the segments connected to the endpoints of thethird segment by hinges. To form a triangle, you need to be ableto swing the segments so that their unhinged endpoints meet but do not lie completely flat. This is possible only if the combined length of the two segments is greater than the length of the third segment. Imagine two segments connected by a hinge.

To form a triangle, youneed to be able to adjust the opening between these sides so that theunhinged endpoints meet the endpoints of the third segment, withoutlying completely flat.



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