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angle J and angle D are at the base of an isosceles triagle hence the two are equal.
17.angle JAC=angle DAC is true since the line AC is perpendicular line dropping from the apex of an isosceles triangle.
18. Is also true since the line AC is a perpendicular line hence both the angles JCA and DCA are 90 degrees.
19. the sum of two right angles is equal to 180 degrees i.e. 90+90=180. and we know angles JCA and DCA are each 90 degrees.
20.Line AJ =Line JD. This is true since the triangle is an isosceles triangle hence both sides are equal.
21.C is the midpoint of JD is also true since the line AC is a perpendicular bisector of the isosceles triangle.
22. Supplementary angles add up to 180 degrees. and angles on a straight line add up to 180 degrees. Hence angles JAE and EAF are adjacent since they are next to each other on a straight line and they add up to 180 degrees.
23. Vertical angles are defined as each of the pairs of opposite angles made by two intersecting lines. Thus angles EAF and JAD are vertical angles.
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