In the given diagram, the size of the angle AEF is 90°
Calculating the measure of an angle
From the question, we are to determine the size of angle AEF
From the given information,
ABCD is square
∴ <DCB = <CBA = = <BAD = <ADC = 90° (Each of the interior angles of a square)
Also,
Triangle DEF is equilateral
∴ <DEF = <EFD = <FDE = 60° (Each interior angle of an equilateral triangle)
Since CDF is a straight line, we can write that
<CDA + <ADE + <FDE = 180° (Sum of angles on a straight line)
Then,
90° + <ADE + 60° = 180°
150° + <ADE = 180°
<ADE = 180° - 150°
<ADE = 30°
Now,
<ADE = <AED (Base angles of an isosceles triangle)
∴ <AED = 30°
In the diagram,
<AEF = <AED + <DEF
∴ <AEF = 30° + 60°
<AEF = 90°
Hence, in the given diagram, the size of the angle AEF is 90°
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