External angle

Geometry Level 2

What is the sum of external angles of a triangle in degrees?


The answer is 360.

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3 solutions

Viki Zeta
Jun 11, 2016

B + x = 180 > 1 A + y = 180 > 2 C + z = 180 > 3 ( 1 ) + ( 2 ) + ( 3 ) = > ( A + B + C ) + x + y + z = 540 = > ( 180 ) + x + y + z = 540 = > x + y + z = 360 \angle B\quad +\quad \angle x\quad =\quad 180\quad \quad ->\quad 1\\ \angle A\quad +\quad \angle y\quad =\quad 180\quad \quad ->\quad 2\\ \angle C\quad +\quad \angle z\quad =\quad 180\quad \quad ->\quad 3\\ \\ (1)\quad +\quad (2)\quad +\quad (3)\\ =>\quad (\angle A\quad +\quad \angle B\quad +\quad \angle C)\quad +\quad x\quad +\quad y\quad +\quad z\quad =\quad 540\\ =>\quad (180)\quad +\quad x\quad +\quad y\quad +\quad z\quad =\quad 540\\ =>\quad x\quad +\quad y\quad +\quad z\quad =\quad 360\\

Moaj Ahmed
Jun 11, 2016

a n g l e X = a n g l e A + a n g l e C angle X = angle A + angle C ; a n g l e Y = a n g l e B + a n g l e A angle Y = angle B + angle A ; a n g l e Z = a n g l e C + a n g l e B angle Z = angle C + angle B ; a n g l e X + a n g l e Y + a n g l e Z = 2 ( a n g l e A + a n g l e B + a n g l e C ) = 360 angle X + angle Y + angle Z = 2(angle A + angle B + angle C) = 360

The answer is 36 0 360^\circ .

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