sinx=(√90)/10
sin(π/4+2x)=sinπ/4cos2x+cosπ/4sin2x
=√2/2(cos2x+sin2x)
=√2/2(2cos²x-1+2sinxcosx)
=√2/2(2*10/100-1+2*√90/10*√10/10)
= - √2/10
已知cos(x)=sqrt(10)/10,x属于(0,pi/2),求sin(pi/4+2x)的值
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