2(sina)^2+3sinacosa-5(cosa)^2=[2(sina)^2+3sinacosa-5(cosa)^2]/[(sina)^2+(cosa)^2]
分子分母同除以(cosa)^2得,[2(tana)^2+3tana-5]/[[(tana)^2+1]
将tana=2代入得,9/5
已知tana=2,求2(sina)^2+3sinacosa-5(cosa)^2
已知tana=2,求2(sina)^2+3sinacosa-5(cosa)^2
数学人气:298 ℃时间:2020-04-15 00:20:13
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