在△ABC中,∠ACB=90°,D为AB中点
=> CD = AD = BD,∠BCD =∠B
tan∠BCD = 1/3,
=> tan∠B = 1/3,cot∠B = 3,sin∠B = 3/√10,cos∠B = 1/√10
=> tan∠C= 3,cot∠C = 1/3,sin∠C = 1/√10,cos∠B = 3/√10