SOLUTION: Given: In triangle ABC, angle B = 120 Proven: angel A (equal sign with a line through it) 60 degrees Plan: Use an indirect poof. (write the proof using the paragraph meth

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Question 111468: Given: In triangle ABC, angle B = 120
Proven: angel A (equal sign with a line through it) 60 degrees
Plan: Use an indirect poof.
(write the proof using the paragraph method) I am totally lost here, could someone help me? That’s my problem with algebra; it all looks like Chinese to me. lol

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

Given: In triangle ABC, angle B+=+120%5E+o
Proven: angel A A is not equal to 60%5E+o

If you use an indirect proof, you need to assume what you need to+prove+is+false, and then show that something contradictory (absurd) happens.
You will need following steps:
Assume that the opposite of what you are trying to prove is true; in
other words, assume that angle is A=60%5E+o

as we know, the+sum+of+all+three+angles of
a triangle is equal to 180%5E+o+degrees.
A+%2B+B+%2B+C+=+180%5E+o
you can solve for C
+C+=+180%5E+o+-+%28A+%2B+B%29
+C+=+180%5E+o+-+%2860%5E+o%2B+120%5E+o%29
+C+=+180%5E+o+-++180%5E+o
+C+=+0+.....it is absurd to have one of three angles in a
triangle equal to 0

So, you can conclude that, as it was proven, angel A is not equal to 60%5E+o