设a属于（0,派/2),若sina=3/5,则根号2cos(a+派/4)等于?

因为 a∈（0,π/2),sina=3/5 所以cosa=4/5 cos(π/4)=sin(π/4)=sqrt(2)/ssqrt(2*cos(a+π/4))=sqrt(2*(cosa*coa(π/4)-sina*sina(π/4)))=sqrt(2*((4/5)*sqrt(2)/2-(3/5)*sqrt(2)/2)=sqrt(2*(sqrt(2)/10)=sqrt(sqrt(2)/5)=sqrt(sqrt(50))/5五分之 四次根号下五十