1/(1-cosaXsina)=(cos^2+sin^2)/(cos^2+sin^2-cos*sin)=(上下含胡同除以cos^2,得)(1+tan^2)/兆老誉(1+tan^2-tan)=(1+9)/(1+9-3)=10/族段7
1/御谈毁(1-cosasina)=(cosacosa+sinasina)/(cosacosa+sinasina-cosasina)=(1+tanatana)/(1+tanatana-tana)=(1+9)/侍散(1+9-3)=10/镇备7
10/7