高等数学基础题求助

2025-05-22 00:06:44
推荐回答(1个)
回答(1):

记 f(x) = (sinx)^3cosx, 则
f'(x) = 3(sinx)^2(cosx)^2 - (sinx)^4
= (sinx)^2(cosx)^2[3-(tanx)^2],
得驻点 x = 0,π/3, π/2, 2π/3, π
f(0) = f(π/2) = f(π) = 0 , f(π/3) = 3√3/16, f(2π/3) = -3√3/16.
故 当 a > 3√3/16 时 , 方程无解,
当 a = 3√3/16 时,方程有唯一解 x = π/3,
当 0 < a < 3√3/16 时,方程有两个解 。