由于三角函数的对应关系不是一一对应 ,所以三角函数在整个定义域上无反函数 ,反三角函数是三角函数在某个单调区间内的反函数 .我们把函数ｙ =ｓｉｎｘ在 - π2 ,π2 ,ｙ =ｃｏｓｘ在 [0 ,π],ｙ =ｔａｎｘ在 - π2 ,π2 ,ｙ =ｃｏｔｘ在 (0 ,π)内的反函数分别称为反正弦函数 Because the correspondence of the trigonometric functions is not a one-to-one correspondence, the trigonometric function has no inverse function over the entire definition domain, and the inverse trigonometric function is the inverse function of the trigonometric function within a monotonous interval. We put the function y = sinx at - π2, π2 y = cosx in [0, π], y = tanx in - π2, π2, y = cotx in (0, π) in the inverse function are called the inverse sine function