Question

一道定积分题目？

请教下画横线部分是怎么转过来的

Answer 1

sint+cost=sint*1+cost*1=√2 * [sint*cos(pi/4)+cost*sin(pi/4)]
=√2 * sin(t+pi/4)
对于盯悉侍隐藏的数字1和0,要更凯吵敏陆世感一点

Answer 2

常用缓启旁的旁碰三角恒等变换，用两角扰橡和公式
sint+cost=√2·(1/√2·sint+1/√2·cost)=√2·[cos(π/4)·sint+sin(π/4)·cost]=√2·sin(π/4+t)