a∈(π/4,π) π/4+a∈(π/2,5π/4)
cos(π/4+a)=-2√2/3
(1)(1+tana)/(1-tana)=(cosa+sina)/(cosa-sina)=sin(π/4+a)/cos(π/4+a)=-√2/4
(2)cos(a-π/4)+sin2a=sin(a+π/4)+[sin(a+π/4)cos(a-π/4)-sin(a-π/4)cos(a+π/4)]
=sin(a+π/4)+[sin(a+π/4)sin(a+π/4)-cos(a+π/4)cos(a+π/4)]=-4/9
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