1)Components of a vector A=A+A A=Ai+A i,j: represent unit vectors in direction of +X-axis or y-axIs 6 A= t80=A,/A,A  A A i A j x y = ˆ + ˆ  2 2 A = A = Ax + Ay   O x y Ay Ax tg = / i j ˆ ， ˆ :represent unit vectors in direction of +x-axis or +y-axis Ax  Ay  A Ax Ay    = + 1) Components of a vector: A A i A A j x x y y ˆ , ˆ = =  