A quadrangle ABCD is inscribed in a circle. The ABD angle is 71 °, the CAD angle is 61 °. Find the angle ABC.

Consider a quadrilateral ABCD, which is inscribed in a circle.

By the condition of the problem, it is known that:

angle ABD = 71 ° and angle CAD = 61 °.

Note that the CAD and CBD corners rest on the same arc. Hence:

angle CAD = angle CBD.

From here we can get:

ABC = ABD + CBD = ABD + CAD = 71 ° + 61 ° = 132 °.

Answer: angle ABC = 132 °.



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