Answer:
Option B
Step-by-step explanation:
The two acute angles of a right triangle are equal.
[tex] \angle \: A + 18 = 180[/tex]
[tex]\angle \: A= 90 - 18 = 72 \degree[/tex]
Recall the mnemonics SOH-CAH-TOA
The tangent ratio is opposite over adjacent.
[tex] \tan(18) = \frac{AC}{21} [/tex]
[tex]AC = 21 \tan(18) [/tex]
[tex]AC = 6.8[/tex]
The sine ratio is opposite over hypotenuse
Using the sine ratio,
[tex] \sin(72) = \frac{21}{AB} [/tex]
[tex]AB = \frac{21}{ \sin(72) } = 22.1[/tex]
