Would you tell me how to achieve this?

> eqn1 := e1*i1 + e2*i2 + e3*i3 = 0
Then, 

solve( { eqn1 } , { i1 } , explicit ) ;
                     /       e2 i2 + e3 i3\ 
                    { i1 = - ------------- }
                     \            e1      / 
Then, I want to replace 'e2/e1' with this expression:

> eqn2 := n12 = e1/e2;

In other words, I want to express the following:

                       /       e2 i2 + e3 i3\ 
                    { i1 = - ------------- }
                     \            e1      / 

as this:

                      /          -i2     - e3 i3\ 
                    { i1 =  ------   + ------ }
                     \            n12        e1   / 

Thank you in advance!

Here are two matrices:

Ts:=matrix([[cos(omega*t), cos(omega*t-2/3*Pi), cos(omega*t+2/3*Pi)], [sin(omega*t), sin(omega*t-2/3*Pi), sin(omega*t+2/3*Pi)],[1/2, 1/2, 1/2]]);
Xin:=matrix([[cos(omega*t+alpha)],[cos(omega*t+alpha-2/3*Pi)],[cos(omega*t+alpha+2/3*Pi)]]);

Then, if I attempt this operation, 'simplify(multiply(Ts, Xin));', this becomes the result:

Matrix(3, 1, [[cos(omega*t)*cos(omega*t+alpha)+cos(omega*t+(1/3)*Pi)*cos(omega*t+alpha+(1/3)*Pi)+sin(omega*t+(1/6)*Pi)*sin(omega*t+alpha+(1/6)*Pi)], [sin(omega*t)*cos(omega*t+alpha)+sin(omega*t+(1/3)*Pi)*cos(omega*t+alpha+(1/3)*Pi)-cos(omega*t+(1/6)*Pi)*sin(omega*t+alpha+(1/6)*Pi)], [(1/2)*cos(omega*t+alpha)-(1/2)*cos(omega*t+alpha+(1/3)*Pi)-(1/2)*sin(omega*t+alpha+(1/6)*Pi)]])

However, if I attempt to reduce each row, the previous result is reduced much further. 

For example, this shows the expand operation applied to the first row and its result.  

expand(3*cos(alpha)*(1/2)+(1/2)*cos(2*omega*t+alpha)-(1/2)*sin(2*omega*t+(1/6)*Pi+alpha)-(1/2)*cos(2*omega*t+(1/3)*Pi+alpha), trig);
                         

3*cos(alpha)*(1/2)

Is there any way to reduce the entire matrix in a similar way, instead of using this element by element operation?