In the given fig,abc is a triangle in which angleA = angleB and AD=BE....
Suppose ABC be a Triangle where Ang.A=Ang.B and D&E are the points on ur figure..Then Clearly AC=BCNOW,we have AD=BEso,AC-AD=BC-BEI.E.CD=CEOR,CD/CE=1ALSO,AC/BC=1SO,CD/CE=AC/BCOR,CD/AC=CE/BCNOW,IN TRIANGLE.CDE AND TRIANGLE.CABCD/AC=CE/BCALSO,ANG.DCE=ANG.ACB (COMMON)SO.BOTH TRIANGLE ARE SIMILAR SO,BY B.P.T...DE PARALLEL AB..
In the given fig,abc is a triangle in which angleA = angleB and AD=BE....
Proof:
Given: In triangle ABC, angle A = angle B and AD = BE.
To prove: DE || AB.
Proof:
Step 1: Draw a line segment CF parallel to DE, intersecting AB at F.
Step 2: Now, we need to prove that DE || AB. To prove this, we will prove that angles ADE and ACF are equal.
Step 3: In triangle ABD, angle A = angle B (Given).
Step 4: In triangle ADE, angle A = angle DAE (Angles opposite to equal sides are equal).
Step 5: In triangle ACF, angle A = angle CAF (Angles opposite to equal sides are equal).
Step 6: From Step 4 and Step 5, we have angle DAE = angle CAF.
Step 7: In triangle ADE, angle DAE = angle ADE (Angle sum property of a triangle).
Step 8: From Step 6 and Step 7, we have angle ADE = angle CAF.
Step 9: From Step 8, we can conclude that angles ADE and ACF are equal.
Step 10: Now, since angles ADE and ACF are equal, it implies that DE is parallel to CF (Alternate Interior Angles Theorem).
Step 11: But CF is parallel to DE, so we can conclude that DE is parallel to AB (Transitive Property of Parallel Lines).
Step 12: Hence, we have proved that DE || AB.
Therefore, in triangle ABC, if angle A = angle B and AD = BE, then DE is parallel to AB.
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