sinA^2+cosA^2=1 sinA+cosA=√2/2.(1)(sinA+cosA)^2=1+2sinAcosA=1/2 得2sinAcosA=-1/2所以(sinA-cosA)^2=1-2sinAcosA=3/2 得sinA-cosA=√6/2.(2)由（1),(2）得sinA=（√6+√2)/4 cosA=(√2-√6)/4所以tanA=sinA/cosA=-(2+√3)
