multiply method
Multiplies this matrix by the given matrix.
Implementation
Matrix3 multiply(Matrix3 o) =>
Matrix3(
a * o.a + b * o.d + c * o.g,
a * o.b + b * o.e + c * o.h,
a * o.c + b * o.f + c * o.i,
d * o.a + e * o.d + f * o.g,
d * o.b + e * o.e + f * o.h,
d * o.c + e * o.f + f * o.i,
g * o.a + h * o.d + i * o.g,
g * o.b + h * o.e + i * o.h,
g * o.c + h * o.f + i * o.i,
);