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)/s
sqrt(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