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若0≤a<π/2,则 sina≤a≤tga.(证略).这个不等式把 a 的三角函数与 a 直接联系起来从而有着重要的作用.例1 对任何∈(0,π/2);下式正确的是( )
If 0 ≤ a < π/2, sina ≤ a ≤ tga. (information omitted). This inequality has a direct effect on the trigonometric function of a and is associated with a. Example 1 For any ∈ (0, π/2) ); The following formula is correct ()