函数y=-1/2cos3x,x属于(π/4,5π/9)的值域是A、-1/4,根号下2/4的闭区间B、-1/4,1/2的左开右闭C、-1/2,根号下2/4的闭区间D、-根号下3/4,1/2的左开右闭

Question

函数y=-1/2cos3x,x属于(π/4,5π/9)的值域是
A、-1/4,根号下2/4的闭区间 B、-1/4,1/2的左开右闭 C、-1/2,根号下2/4的闭区间 D、-根号下3/4,1/2的左开右闭

Answer 1

D