sin（a-π/4）=7√2/10 cos（a-4/π）=√2/10 sin（2a-2/π）=2sin（a-π/4）cos（a-4/π）=7/25
cos2a=-7/25 sin2a=-24/25 tan2a=24/7 tan（2a+4/π）=（tan2a+1）/（tan2a-1）=31/17