how do I know where which choices below go into the correct blanks?
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In a 30-60-90 special right triangle, we have the following.
If the short leg is 7 cm, then x = 7.
So, the hypotenuse would be
[tex]h=2x=2(7)=14\operatorname{cm}[/tex]The length of the long leg is
[tex]x\sqrt[]{3}=7\sqrt[]{3}\approx12.12\operatorname{cm}[/tex]