如何求证：(sinA/ cosA)^2+(sinB/ cosB)^2=(cosA/ sinB)^2
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c=AB=√2
tanA=2, tanB=3
cosA = 1/√5
tanA + tanB =5
sinA/cosA + sinB/cosB =5
sin(A+B)/(cosAcosB)=5
sin(A+B) =5cosAcosB
sinC =5cosAcosB
AC=b
b/sinB= c/sinC
b/sinB=√2/(5cosAcosB)
b= (√2/5)tanB/cosA
= (√2/5)(3)√5
= (3/5)√10
AC=b=(3/5)√10
tanA=2, tanB=3
cosA = 1/√5
tanA + tanB =5
sinA/cosA + sinB/cosB =5
sin(A+B)/(cosAcosB)=5
sin(A+B) =5cosAcosB
sinC =5cosAcosB
AC=b
b/sinB= c/sinC
b/sinB=√2/(5cosAcosB)
b= (√2/5)tanB/cosA
= (√2/5)(3)√5
= (3/5)√10
AC=b=(3/5)√10
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