AC Lim's answer to :)'s Primary 5 Maths Angles & Geometry Singapore question.
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Hope this helps
Date Posted:
4 years ago
The tutor’s answer is correct.
Looking at line CD, the sum of all the angles on the bottom side of line CD must equal 180 degrees.
Angle COB
= 63 + 74
= 137 degrees
Angle BOD
= 180 - 137
= 43 degrees
because the sum of angles along that side of line CD is equal to 180 degrees.
Looking at line AB, the sum of angles on the top side of the line must be equal to 180 degrees.
There is an angle 90 degrees there, an angle 43 degrees which we just found and an angle c.
Angle c
= 180 - 90 - 43
= 47 degrees
because the sum of angles on that side of line AB is 180 degrees.
The tutor has explained this (though in a condensed format on the diagram).
Looking at line CD, the sum of all the angles on the bottom side of line CD must equal 180 degrees.
Angle COB
= 63 + 74
= 137 degrees
Angle BOD
= 180 - 137
= 43 degrees
because the sum of angles along that side of line CD is equal to 180 degrees.
Looking at line AB, the sum of angles on the top side of the line must be equal to 180 degrees.
There is an angle 90 degrees there, an angle 43 degrees which we just found and an angle c.
Angle c
= 180 - 90 - 43
= 47 degrees
because the sum of angles on that side of line AB is 180 degrees.
The tutor has explained this (though in a condensed format on the diagram).
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