若sin(π+a)=1/根号10,则sec(-a)+sin(-a-90°)/csc(540°-a)-cos(-a-270°)的值A,-1/3 B,+-1/27 C,1/3 D-根号3/3
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![若sin(π+a)=1/根号10,则sec(-a)+sin(-a-90°)/csc(540°-a)-cos(-a-270°)的值A,-1/3 B,+-1/27 C,1/3 D-根号3/3](/uploads/image/z/2495647-55-7.jpg?t=%E8%8B%A5sin%28%CF%80%2Ba%29%3D1%2F%E6%A0%B9%E5%8F%B710%2C%E5%88%99sec%28-a%29%2Bsin%28-a-90%C2%B0%29%2Fcsc%28540%C2%B0-a%29-cos%28-a-270%C2%B0%29%E7%9A%84%E5%80%BCA%2C-1%2F3+B%2C%2B-1%2F27+C%2C1%2F3+D-%E6%A0%B9%E5%8F%B73%2F3)
若sin(π+a)=1/根号10,则sec(-a)+sin(-a-90°)/csc(540°-a)-cos(-a-270°)的值A,-1/3 B,+-1/27 C,1/3 D-根号3/3
若sin(π+a)=1/根号10,则sec(-a)+sin(-a-90°)/csc(540°-a)-cos(-a-270°)的值
A,-1/3 B,+-1/27 C,1/3 D-根号3/3
若sin(π+a)=1/根号10,则sec(-a)+sin(-a-90°)/csc(540°-a)-cos(-a-270°)的值A,-1/3 B,+-1/27 C,1/3 D-根号3/3
sin(π+a)=1/√10,则sina=-1/√10
[sec(-a)+sin(-a-90°)]/[csc(540°-a)-cos(-a-270°)]
=(-1/cosa-cosa)/(1/sina-sina)
={[1-(cosa)^2]/cosa}/{[1-(sina)^2]/sina}
=[(sina)^2/cosa]/[(cosa)^2/sina]
=(sina)^3/(cosa)^3
=(tana)^3
.
[sin(-a)+sin(-a-90°)]/[cos(540°-a)-cos(-a-270°)] =(-sina-cosa)/[cos(180°-a)-cos(270°+a)] =-(sina+cosa)/(-cosa
[sin(-a)+sin(-a-90°)]/[cos(540°-a)-cos(-a-270°)]
=(-sina-cosa)/[cos(180°-a)-cos(270°+a)]
=-(sina+cosa)/(-cosa-sina)
=(sina+cosa)/(cosa+sina)
=1