how can you prove that sum of all angle of an triangle is180?
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draw a perpendicular on the line then add both sides 90+90
tarika017:
because of Angle Sum property of triangle which says that sum of all angle is equal to 180 degree
ok
oo
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Consider triangle PQR,
Draw a line XY passing through P parallel to QR,
PQ is the transversal of lines XY & QR,
angle PQR = angle XPQ (alternate angles) ---->(equation 1)
angle PRQ = angle YPR (alternate angles) ---->(equation 2)
angle QPR + angle XPQ + angle YPR = 180 degree (linear pair)
Therefore, angle QPR + angle PQR + angle PRQ = 180 degree [ from equations (1) & (2) ] .
Draw a line XY passing through P parallel to QR,
PQ is the transversal of lines XY & QR,
angle PQR = angle XPQ (alternate angles) ---->(equation 1)
angle PRQ = angle YPR (alternate angles) ---->(equation 2)
angle QPR + angle XPQ + angle YPR = 180 degree (linear pair)
Therefore, angle QPR + angle PQR + angle PRQ = 180 degree [ from equations (1) & (2) ] .
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