BGA and BFC are straight lines.
EFG and DCA are parallel lines.
Show that triangle ABC is isosceles.
Give a reason for each stage of
your working.
A
Angle BAC 48 because corresponding angles are equal
180-114-66 because angles on a straight line add to 180°
GAC = 48 because corresponding angles are
equal
=
GFC 114 because vertically opposite angles are equal
FCA = 66° because co-interior angles add up
to 180°
Therefore, ABC is an isosceles triangle
B
G/48
114
F
E
C
D
Answer (2)
Triangle ABC is isosceles because it has two equal angles (66° each), which means two of its sides are equal. ;
Triangle ABC is isosceles because it has two angles measuring 66°, which makes two sides of the triangle equal. The angles were determined using the properties of parallel lines and angles on a straight line. Each step used a specific reason linked to angle relationships.
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