Which of the following best explains why a complex number z = a bi and its polar form represent the same number?
A. by definition, cosine (theta) = startfraction r over a endfraction and sine (theta) = startfraction r over b endfraction.
B. by definition, cosine (theta) = startfraction r over b endfraction and sine (theta) = startfraction r over a endfraction.
C. by definition, cosine (theta) = startfraction a over r endfraction and sine (theta) = startfraction b over r endfraction.
D. by definition, cosine (theta) = startfraction b over r endfraction and sine (theta) = startfraction a over r endfraction.