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数学
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将△ABC绕点C按顺时针方向旋转20°,点B落在点B′处,点A落在点A′处,若AC⊥A′B′,则∠BAC=______.
人气:413 ℃ 时间:2019-10-11 09:39:13
解答
∵△ABC绕点C按顺时针方向旋转20°,点B落在点B′处,点A落在点A′处,
∴∠BCB′=20°,△ABC≌△A′B′C,
∴∠BAC=∠A′,∠ACB=∠A′CB′,
∴∠BCB′=∠ACA′=20°,
∵A′B′⊥AC,
∴∠A′EC=90°,
∴∠A′=180°-90°-20°=70°,
∴∠BAC=70°,
故答案为:70°.
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