Trigonometric Ratios: Sin? Cos? Tan? Angles?

In my textbook, it askes:
Using the exact values, show that sin ? / cos ? = tan ? for each angle.
a) ? = 30°

I know
Sin 30° = 1/2
Cos 30° = ?3/2
Tan 30° = ?3/3 (answer)

But I don't understand how to add/subtract, multiply/divide the numbers/fractions. Can someone show me step by step how to get the answer?
 
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