22.AOB is a straight line oC and OD are the rays on it. Such that <AOC +<BOD=90° Find <COD.
23.Prove that the straight lines perpendicular to the same straight line are parallel to one
another.
24.If the bisectors of the angles of B and C intersect at point O.Show that L BOC=90° +1/2
<A.
25. Bisectors of interior <B and exterior angle <ACD of triangle ABC intersect at point
T.Prove that <BAC=2<BTC.
26.Prove that the two lines that are resp.perpendicular to two intersecting lines intersect each
other.
27.Prove that in a triangle must have atleast two acute angles.
28.Prove that the sum of all the interior angles of a triangle is 180°.Find the angles of a
triangle if the ratio of the angle is 1:2:1.
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