Two supplementary angles are congruent. Which equation gives the measure in degrees, d, of each angle? CLEAR CHECK d + 2d = 180 2d = 180 d + d = 90 No equation because supplementary angles cannot be congruent.

cause and effect concave lenses side of lenses are curved inward

< coa = 150 ( given)

as ba and bc are tangents

so oc and oa is perpendicular to cb and ab respectively because in circle normal passes through centre

so in quadrilateral oabc

< coa + < oab + < ocb + < abc = 360

150 +90+90 + < abc = 360

330 + < abc = 360

< abc = 360 -330 = 30

so < abc = 30

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