In the diagram below, ABCD and DEFG are congruent squares, and angle CDG is 60°.

What is angle ACF?

Answer is 90 deg.

join CG hence forming an equilateral triangle DCG

CG=GF

and angle CGF = 60+90 = 150

so angle FCG = 15

hence angle DCF is 45 which implies angle ACF must be 90 deg.

Answer is obvious from the construction itself !!

Posted by Rosy on 2009-04-20 13:47:18