5.计算 (1) 解:原式=44°78′-36°56′ =8°22′ (2) 解:原式=45°90′ =46°30′ 6.根据图形填空 (1)∠DOB,∠AOC (2)∠AOB,∠COD 素养提升 7. (1)解:∠BAE=∠CAD, 理由:因为∠BAD=∠CAE 所以∠BAD+∠DAE=∠CAE+∠DAE, 所以∠BAE=∠CAE (2)解:因为∠BAD=∠CAE, 所以∠BAD=24°48′ 所以∠CAD=∠BAC-∠BAD =106°-24°48′ =105°60′-24°48′ = 81°12'. |