cos∠adc=3/5
cos∠adc=CD/AD=CD/(CD+4)=3/5 3cd+12=5cd=6
(2)
ac=根号(ad²+cd²)
=根号(100-36) =8
bc=10
所以:ab=根号(100+64)=2根号41
sinB=Ac/ab=8/2根号41
=4/根号41
cos∠adc=3/5
cos∠adc=CD/AD=CD/(CD+4)=3/5 3cd+12=5cd=6
(2)
ac=根号(ad²+cd²)
=根号(100-36) =8
bc=10
所以:ab=根号(100+64)=2根号41
sinB=Ac/ab=8/2根号41
=4/根号41