Question

已知B为锐角,且sinB+cosB=4/3,求sinB×cosB的值

Answer 1

(sinB+cosB)^2=(sinB)^2+(cosB)^2+2*sinB*cosB=(4/3)^2=16/9

因为（sinB)^2+(cosB)^2=1

所以2*sinB*cosB=16/9-1=7/9

所以sinB*cosB=7/18