Q.Two circles touch each other externally at point \(C\). \(AB\) is a common tangent to the two circles, touching them at points \(A\) and \(B\), respectively. The measurement of \(\angle ACB\) is – (a) 60° (b) 45° (c) 30° (d) 90°
Answer: D
AP = PC
∴ \(\angle A = \angle PCA\)
Similarly, \(\angle B = \angle PCB\)
\(\angle ACB = \angle PCB + \angle PCA = \angle A + \angle B\)
In \(\triangle ABC\), \(\angle A + \angle B + \angle C = 180°\)
or, \(\angle A + \angle B + \angle A + \angle B = 180°\)
or, \(\angle A + \angle B = 90°\)
∴ \(\angle ACB = \angle A + \angle B = 90°\)
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