高一数学题目.写过程,谢谢!

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(1) B=π/4 AC=2√5 cosC=2√5/5
sinC=√(1-cos²C)=√5/5
sinA=sin[180°-(B+C)]
=sin(B+C)
=sinBcosC+cosBsinC
=√2/2x2√5/5+√2/2x√5/5
=3√10/10
(2) a/sinA=b/sinB
a=bsinA/sinB=2√5x3√10/10/(√2/2)
=6c=bsinC/sinB=(2√5x√5/5)/(√2/2)
=2√2AD²=(a/2)²+c²-2(a/2)c cosB
=9+8-3√2x2√2
=5ad=√5======以下答案可供参考======
供参考答案1:
由cosC可知sinC，又知cos45和sin45，而sinA=sin(C+45)用公式就可推出