How many 4-digit personal identification numbers are possible if the number  cannot  contain a zero?
a.
5,040
b.
6,561
c.
9,000
d.
10,000

Hello! i hope this
since the cosine is the ratio of the adjacent side to the hypotenuse, you can see that cos 60° = ½. answer. according to the property of cofunctions (topic 3), sin 30° is equal to cos 60°. sin 30° = ½.

step-by-step explanation:

only stephen hawking would know.