△ABC中,B=π/4,c=根号2,a=3求sinA

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△ABC中,B=π/4,c=根号2,a=3求sinA
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△ABC中,B=π/4,c=根号2,a=3求sinA
△ABC中,B=π/4,c=根号2,a=3求sinA

△ABC中,B=π/4,c=根号2,a=3求sinA
b²=a²+c²-2accosB
=3²+√2²-2*3*√2*cosπ/4
=9+2-6*√2*√2/2
=11-6
=5
b=√5
a/sinA=b/sinB
3/sinA=√5/sinπ/4
sinA*√5=3*√2/2
sinA=(3√2/2)/√5
=(3√2/2)*(√5/5)
=3√10/10