In the circle O, M is the middle point of the chord AB, passing through the point B as the tangent of the circle O, and intersecting with the extension line of OM at the point C. proof 1: angle a = angle C. If OA = 5, OB = 8, find OC
If ob is connected, then ∠ OBC = 90, ∠ a = oba
∴∠AOM=∠ABC
The four points of acbo are in the same circle (the same circle angle of the same arc)
∴∠A=∠C
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