cosa=1/3
sina=-2√2/3
tana=-2√2
tan（π/4+a）
=(tanπ/4+tana)/(1-tanπ/4tana)
=(1+tana)/(1-tana)
=(1+tana)/(1-tana)
=(1-2√2)/(1+2√2)
=(1-2√2)^2/(1+2√2)(1-2√2)
=(9-4√2)/(-7)
=(4√2-9)/7