作业帮函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ).函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ). A:10. B:11C:12. D:13
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![函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ).函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ). A:10. B:11C:12. D:13](/uploads/image/z/9294545-65-5.jpg?t=%E5%87%BD%E6%95%B0y%3D%5B1%2F%28sin%5E2%26%238226%3BX%29%5D%2B%5B4%2F%28cos%5E2%26%238226%3BX%29%5D%2B3%E7%9A%84%E6%9C%80%E5%B0%8F%E5%80%BC%E4%B8%BA%28.+%29.%E5%87%BD%E6%95%B0y%3D%5B1%2F%28sin%5E2%26%238226%3BX%29%5D%2B%5B4%2F%28cos%5E2%26%238226%3BX%29%5D%2B3%E7%9A%84%E6%9C%80%E5%B0%8F%E5%80%BC%E4%B8%BA%28.++++%29.++A%3A10.+++++++++B%3A11C%3A12.+++++++++D%3A13)
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函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ).函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ). A:10. B:11C:12. D:13
函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ).
函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ).
A:10. B:11
C:12. D:13
函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ).函数y=[1/(sin^2•X)]+[4/(cos^2•X)]+3的最小值为(. ). A:10. B:11C:12. D:13
应选C.
y=1+(cotx)^2+4+4(tanx)^2+3=8+(cotx)^2+4(tanx)^2≥8+2√[(cotx)^2·4(tanx)^2]
=8+4=12