Bl8de

happypoppy:

Hi Bl8de,


It was given in the question that AD = AC = AB.

Since AC is perpendicular to BD, AC = KL (which in turn) = LM (as this is a square) = BD (question states that ML and BD are parallel).

Once it has been established that BD = AD = AB, triangle ADB is essentially an equilateral triangle. Therefore angle DAB = 60 degrees and angle DAC = 60 degrees / 2 = 30 degrees.

In view that triangle DAC is an isosceles triangle, angle b = 75 degrees and the required angle DCB = 75 degrees x 2 = 150 degrees.


NB: BTW, it was DH that solve the question for me. I was mulling over it for ages when he came over and solve it in 5 mins flat! I guess geometry is one of those questions that either you have the flair for it or you dont.

Did the question state that i is a square? Because I still dont see why KL = LM. There is no specific evidence for that.

Ultra KS:

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May I know how did you derive ML = LK and AC?