如图所示，皮带轮半径为R，皮带的拉力分别为T1和T2，若T1、T2的大小不变，皮带的包角为<img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/10587a5b181f4f8697d578e16dfbeead.png?x-oss-process=image/sharpen,200"/>，则 <img src="http://jgxm-question.oss-cn-beijing.aliyuncs.com/psst/files/f4e494801ee04275aaf1b9000cc095aa.png?x-oss-process=image/sharpen,200"/