已知随机变量X在<img src="https://static.zxtiku.com/wangke/imgs/topic/aff8fe84c505a4d302e9324a46d4b329.png"/> 上服从均匀分布,随机变量Y在<img src="https://static.zxtiku.com/wangke/imgs/topic/8fc734fa81c080c8aa648ca3e25bb1be.png"/> 上服从均匀分布,则<img src="https://static.zxtiku.com/wangke/imgs/topic/87c39bb483df103229827228755d0300.png"/> 在<img src="https://static.zxtiku.com/wangke/imgs/topic/dc54ff9839b473e51fdbf25cad8acbd4.png"/> 时等于( )