Answers

2014-09-19T19:03:23+05:30
By angle sum property the sum of a+b+c=180
In a equilateral triangle all sides are equal
so, a=b=c
a+a+a=180
3a=180
a=180/3
a=60
Hence proved
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The Brainliest Answer!
2014-09-19T19:07:02+05:30
Consider ΔABC with BC as base. AB = BC = CA
Draw a line PQ through A parallel to BC.
Then, angle PAB = angle ABC (alternate interior angles) - 1
Similarly, angle QAC = angle ACB - 2

angle PAB + angle BAC + angle CAQ = 180 (sum of angles on a line)
Then, from 1 and 2,

angle ABC + angle BAC + angle ACB = 180
angle ABC = BAC = ACB (equilateral triangle)
3 * any one of these angles equal = 180
each angle = 180/3 = 60

Thus proven.
Hope it is enough and you understood.
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