Q. In the given figure, AB is the diameter and ADC = 2 times BDC. If BCD = 70 ° , then find the angle made by AC at the centre of the circle.



Let BDC = x, then ADC = 2xNow, ADC + BDC = 180°  Linear pair2x + x = 180°3x = 180°x = 60°So, BDC = 60°Now, in DCB,BDC + BCD + CBD = 180°  Angle sum property60° + 70° + CBD = 180°CBD = 50°Now, angle subtended by an arc at the centre is double the angle subtended by same arc at any point on the circle.So, AOC = 2ABC = 2×50° = 100°

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4cm
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Stop guessing. How could an angle's measure be 4cm?
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