How can I solve the values of the equations?

(The question had been editted again!)a is the angle of the homogeneous object, which is progressive increase that varies from 0°，1°，2°……90°. The equations(which called nonlinear equations with variable coefficients) is vary with the value of a。

r×V-G=0
(V×y1— G×y2÷r)+( V×z1— G×z2÷r)×tan a=0
(V×x1— G×x2÷r)+( V×z1— G×z2÷r)×tan w=0
V and G is the volume and weight of the object. w is an angle variable；The shape of the object change along with a and w； x1 y1 z1 is the centroid of the object ；So every value of a corresponds with one value of centroid. The other terms are constant terms.（ I just want to know the calculation method of the equations，I think the relation of a and x1，y1 ，z1 is not need to be given）
How can I obtain the values of x1，y1 ，z1 and w when the values of a varies from 0°，1°，2°……90°?