#andy
a, góc `B=50=>` góc `C=40`
`sin B = AC/BC=> BC=16,97`
`tan B= AC/AB=> AB=10,91`
`b, C=40=> B=50`
`sin B=AC/BC=> AC=6,13`
`tan B= AC/AB=> AB=5,14`
`c, BC^2=AC^2+AB^2=> AB=15`
`sin B= AC/BC=> B=67,38=> C=22,62`
`d, BC^2= AC^2+AB^2`
`=> AC=3 √3`
`sin B= AC/BC`
`=> B=60=> C=30`