The definition of an angle uses the undefined term

 line segment RS is the sum of two segments RP and PS if point P is between R and S so that RP+PS=RS. Ray. ... a set of points that is the union of rays having the same endpoint. Straight Angle. an angle that is the union of opposite rays (180)

Africans learned what the europeans wanted them to learn. instead of learning about african history and current information that could and would them they learned solely what europe wanted them to. and not everyone received the same education, some received better and others none.