Sides AB and AC of ΔABC are extended to pts P and Q respectively. Also angle PBC is less than angle QCB. Show that AC is greater than AB.
SUPER URGENT!!!! PLEASE!!!!!
Adithya1234:
is it frm congruent triangles?
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Answered by
2
Let angle ABC be called B and angle ACB be called C.
Let angle PBC be called B' and angle QCB be called C'.
B' < C' (B' is less than C') ----(1)
B' = 180 - B, C = 180 - C,
Substituting in (1),
180 - B < 180 - C
OR - B < - C
OR B > C (B is greater than C)
In a triangle, side opposite the greater angle is greater than the side opposite the smaller angle,
Hence side AC (opposite B, greater angel) > side AB (opposite C,smaller angle)
Let angle PBC be called B' and angle QCB be called C'.
B' < C' (B' is less than C') ----(1)
B' = 180 - B, C = 180 - C,
Substituting in (1),
180 - B < 180 - C
OR - B < - C
OR B > C (B is greater than C)
In a triangle, side opposite the greater angle is greater than the side opposite the smaller angle,
Hence side AC (opposite B, greater angel) > side AB (opposite C,smaller angle)
Answered by
4
See the diagram.
Angle PBC < angle QCB
So, x < y
So, 180 - x > 180 - y
Angle ABC > angle ACB
So, angle B > angle C
Now we will prove that AC > AB.
Draw a line BD from B such that the angle ABD is equal to angle C.
Draw a line BE from B such that the angle ABE is equal to (B+C)/2.
Angle ABE = (B+C)/2 and
angle AEB = 180 - A - angle ABE = 180 - A - (B+C)/2
= 180 - (180- B - C) - (B+C)/2 = (B+C)/2 = angle ABE
So , ABE is an isosceles triangle. Sides AB = AE. Now,
AC = AE + EC
AC - AB = AE + EC - AB = EC > 0
So AC > AB
Angle PBC < angle QCB
So, x < y
So, 180 - x > 180 - y
Angle ABC > angle ACB
So, angle B > angle C
Now we will prove that AC > AB.
Draw a line BD from B such that the angle ABD is equal to angle C.
Draw a line BE from B such that the angle ABE is equal to (B+C)/2.
Angle ABE = (B+C)/2 and
angle AEB = 180 - A - angle ABE = 180 - A - (B+C)/2
= 180 - (180- B - C) - (B+C)/2 = (B+C)/2 = angle ABE
So , ABE is an isosceles triangle. Sides AB = AE. Now,
AC = AE + EC
AC - AB = AE + EC - AB = EC > 0
So AC > AB
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