`a)`
Ta có `\hat{xAy} < \hat{xAZ}` ( do ` 50^0 < 70^0` )
` => Ay` nằm giữa ` Ax ; Az`
`b)`
Vì ` Ay` nằm giữa ` Ax ; Az`
` => \hat{xAy} + \hat{yAz} = \hat{xAz}`
` => \hat{yAz} = \hat{xAz} -\hat{xAy} = 70^0 -50^0 = 20^0`
`c)`
Vì `\hat{xAy}` kề bù `\hat{yAm}` nên
` \hat{xAy} + \hat{yAm} = 180^0`
` => \hat{yAm} = 180^0 - \hat{xAy} = 180^0 -50^0 = 130^0`
Vậy ` \hat{yAm} = 130^0`