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    OlympiadEasyGeometry7–9

    In triangle ABCABC the angle at AA measures 40∘40^\circ. The bisectors of the angles at BB and at CC meet at II. How many degrees does angle BICBIC measure?

    No triângulo ABCABC, o ângulo em AA mede 40∘40^\circ. As bissetrizes dos ângulos em BB e em CC encontram-se em II. Quantos graus mede o ângulo BICBIC?

    Triangle ABC, with the angle at A marked 40 degrees. The angle at B is cut into two equal parts by a dashed line running to a point I inside the triangle, and the angle at C is cut into two equal parts by a dashed line running to the same point I. The angle BIC, between the two bisectors, is marked with a question mark.40°?ABCI

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    Solution

    Step 1 of 3

    1. 1.The angles at BB and CC add to 180∘−40∘=140∘180^\circ - 40^\circ = 140^\circ, so their halves add to 70∘70^\circ.