(1除以cos80平方-1除以cos10平方)乘以 1除以cos20 答案最后是32,
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![(1除以cos80平方-1除以cos10平方)乘以 1除以cos20 答案最后是32,](/uploads/image/z/1256088-48-8.jpg?t=%281%E9%99%A4%E4%BB%A5cos80%E5%B9%B3%E6%96%B9-1%E9%99%A4%E4%BB%A5cos10%E5%B9%B3%E6%96%B9%29%E4%B9%98%E4%BB%A5+1%E9%99%A4%E4%BB%A5cos20+%E7%AD%94%E6%A1%88%E6%9C%80%E5%90%8E%E6%98%AF32%2C)
(1除以cos80平方-1除以cos10平方)乘以 1除以cos20 答案最后是32,
(1除以cos80平方-1除以cos10平方)乘以 1除以cos20
答案最后是32,
(1除以cos80平方-1除以cos10平方)乘以 1除以cos20 答案最后是32,
原式=[1/cos^2 (90-10) -1/(cos10)^2]× 1/cos20
=[1/(sin10)^2 -1/(cos10)^2]×1/cos20
=[(cos10)^2-(sin10)^2 / (sin10cos10)^2]× 1/cos20
=[cos20 /(1/2 sin20)^2]× 1/cos20
=1/(1/4)(sin20)^2
=4/(sin20)^2
≈34
[1/(cos80)^2-1/(cos10)^2]*(1/cos20)
=[(cos10)^2-(cos80)^2]/[(cos80)^2*(cos10)^2*cos20]
=[(cos10)^2-(sin10)^2]/[(cos80)^2*(cos10)^2*cos20]
=cos20/[(cos80)^2*(cos10)^2*cos20]
=1/[(sin10)^2*(cos10)^2]
=4/(2sin10cos10)^2
=4/(sin20)^2
最后答案是34.19452826......吧
∵cos80=sin10
∴
[1/(cos80)^2-1/(cos10)^2]*(1/cos20)
=[(cos10)^2-(sin10)^2]/[(sin10)^2*(cos10)^2] *1/cos20
=1]/[(sin10)^2*(cos10)^2]
=4/(sin20)^2
得不到具体的整数啊
不清楚表达式是怎样的,能否有数学表达式写出来呢?