Mak, Ivan's answer to Mandy's Primary 5 Maths Angles & Geometry Singapore question.
Just a note, be careful that your concept of ∠ACB=∠ACD is incorrect Please note! :)
Triangle BCD is an isosceles, that means that BC = CD and ∠DBC = ∠BDC only!
Triangle BCD is an isosceles, that means that BC = CD and ∠DBC = ∠BDC only!
I'm sorry @Ms Jaslyn Lim, but your answer ∠BDC = 53 degrees is not correct.
We know that triangle ACB is an equilateral triangle, i.e. AB= AC= BC and triangle BCD is an isosceles triangle, i.e. BC=CD.
Hence we know that AC = CD. That is, ACD is an isosceles triangle (triangle with two equal sides is ALWAYS an isosceles). i.e. ∠DAC = ∠ADC = 53 degrees.
Hence ∠ACD = 180-53-53=74 degrees.
∠DBC = BDC = (180-60-74)/2=23 degrees.
I have mathematical proofing for my answer. Can you show proof for your answer?
We know that triangle ACB is an equilateral triangle, i.e. AB= AC= BC and triangle BCD is an isosceles triangle, i.e. BC=CD.
Hence we know that AC = CD. That is, ACD is an isosceles triangle (triangle with two equal sides is ALWAYS an isosceles). i.e. ∠DAC = ∠ADC = 53 degrees.
Hence ∠ACD = 180-53-53=74 degrees.
∠DBC = BDC = (180-60-74)/2=23 degrees.
I have mathematical proofing for my answer. Can you show proof for your answer?
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