Home page for accesible maths Math 101 Chapter 4: Taylor series and complex numbers

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4.30 Rules for addition and multiplication

The following hold for all complex z,w,tz,w,t:

(i) Addition is associative (z+w)+t=z+(w+t);(z+w)+t=z+(w+t);

(ii) multiplication is associative (z⁢w)⁢t=z⁢(w⁢t)(zw)t=z(wt);

(iii) addition is commutative z+w=w+zz+w=w+z;

(iv) multiplication is commutative z⁢w=w⁢zzw=wz;

(v) multiplication is distributive over addition t⁢(w+z)=t⁢w+t⁢zt(w+z)=tw+tz;

(vi) 0=0+i⁢00=0+i0 satisfies 0+z=z0+z=z;

(vii) (x+i⁢y)+(-x-i⁢y)=0(x+iy)+(-x-iy)=0;

(viii) 1=1+i⁢01=1+i0 satisfies 1⁢z=z1z=z;

(ix) z⁢w¯=z¯⁢w¯\overline{zw}=\bar{z}\bar{w};

(x) z+w¯=z¯+w¯\overline{z+w}=\bar{z}+\bar{w};

(xi) the conjugate of z¯\bar{z} is zz itself;

(xii) |z|2=z⁢z¯>0|z|^{2}=z\bar{z}>0 for all z≠0z\neq 0.