Polygons and Angles

Geometry Level pending

What is the sum of the measure of angle H and angle I if line AP is parallel with line FH?

note: Diagram is quite not accurate


The answer is 315.

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1 solution

Emmanuel David
Apr 29, 2014

Since Triangle ENF is isosceles, A pair of its angles are equal (N and F). FEN=80, so N+F=180-80. So 50 each. DEN is 60 so GEF is 40. GF) is 30 so EFG is 100. So FGE is 40.

BG is transversal of parallel lines CJ and HF. So CDE is 140. DGH is 140 too because they're alternate interior angles and alternate interior angles are congruent.

Emmanuel David - 7 years, 1 month ago

EDJ is 40 because FGE and EDJ are alternate interior angles. BCD is also isosceles. CDB is 40 because CDB and EDJ are vertical angles. So, DBC is 40 too and C=180-40-40=100.

Emmanuel David - 7 years, 1 month ago

BDM is 90. DBA is also 90 because MD and AB are parallel lines. Angle CDB+MDB=130. LAB is 130 too because they are opposite with D. CBD+ABD=130 too. LMD is 130 also. L is 100

Emmanuel David - 7 years, 1 month ago

to prove I am right, a hexagon's interior angles sum up to 720 degrees. 100+130+130+130+130+100=720

Emmanuel David - 7 years, 1 month ago

We can say that AP is a straight line because it has a parallel. MLK=30. KLP=180-100-30=50. Angle P is 70. LKP=180-70-50=60. KLMDJ is a pentagon that means that its interior angles sum up to 540 degrees.

Emmanuel David - 7 years, 1 month ago

Measures of the angles of pentagon KLMDJ

K=tKL is the exterior angle of triangle KLP and it is equal to 120 because LPK+KLP=120. (a measure of an exterior angles is the sum of its remote interior angles).

L= 30 (given)

M=360-130=230.

D=BDJ and CDG are vertical angles and vertical angles are congruent. BDJ=BDM+MDJ so MDJ=BDJ-BDM which is 140-90=50

point J/ angle t=AP and FH are parallel. CJ and FH are parallel. AP and CJ are parallel (Transitivity). P and t are Consecutive interior angles so they sum up to 180. t=180-P so t=180-70=110 (though t in the image looks like acute angle).

120+30+230+50+110=540

Emmanuel David - 7 years, 1 month ago

r+u+s+t+Q+J=360

pairs of vertical angles r and s t and u J and Q

r+s+u=160

160+t=160+110=270

360-270=90

90/2=45

J=45

Emmanuel David - 7 years, 1 month ago

We are now in Pentagon JIHGD

D=40

G=140

J=45

H+I=540-40+140+45=540-225

H+I=540-225=315

Emmanuel David - 7 years, 1 month ago

Where is angle H and where is angle I.

Anuj Shikarkhane - 6 years, 11 months ago

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