Question 202822: I would appreciate help with this, I am on the SECOND semester of this class, due to this proof and I am about to run out of time. I have submitted this 4x and each time it is wrong. Please help me out, thanks!
Prove: If the base angles of a triangle are congruent, then the triangle is isosceles.
Given: Triangle BAC with angle B = angle C
To Prove: Triangle is isosceles.
Construction:
Draw a perpendicular line from vertex A on side BC which meets side BC at L.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Prove: If the base angles of a triangle are congruent, then the triangle is isosceles.
Given: Triangle BAC with angle B = angle C
To Prove: Triangle is isosceles.
Construction:
Draw a perpendicular line from vertex A on side BC which meets side BC at L.
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Draw triangle ABC with B = C
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Draw a perpendicular from A to side BC forming Angle ALB and Angle ALC
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Prove ABC is isosceles.
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Proof:
B = C---------------------------Given
Angle ALB1 = Angle ALC = 90-----def of perpendicular line
AL = AL-------------------------identity
tri LBA congruent to tri LCA----angle-side-angle theorem
BA = CA-------------------------corresponding parts of congruent triangles
tri ABC is isosceles------------definition of isosceles triangle
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Cheers,
Stan H.
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