Geometry Problem 1508. Post your solution in the comment box below.

Level: Mathematics Education, K-12 School, Honors Geometry, College.

Details: Click on the figure below.

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Note that triangle ABC is equilateral and triangle ACD is isosceles. So angle BCD=120 degrees

ReplyDeleteI believe there may be a small mistake in your answer.

DeleteYes Antonio. I made a mistake angle BCD= 60+80= 140

DeleteTriangle ABC is equilateral and Triangle ACD is thus isosceles (80-20-80)

ReplyDeleteHence < C = 60 + 80 = 140

Sumith Peiris

Moratuwa

Sri Lanka

Some interesting results

Delete1) If BC and AD meet at X, then Tr. CDX is isoceles (40-40-100)

2) If AB, DC meet at Y then Tr. AYD is isoceles 80-20-80

3) The diagonals of ABCD cut at an angle of 70