Answer:
5.2
Explanation:
You want the length of the leg marked x in the 30°-60°-90° right triangle with short leg 3.
Special triangle
The 30°-60°-90° right triangle is one of two "special" right triangles. The ratios of side lengths in this special triangle, shortest-to-longest are ...
1 : √3 : 2
These correspond to ...
3 : x : hypotenuse
Clearly, the side lengths for this triangle can be found by multiplying the basic ratio by 3:
3 : 3√3 : 6
So, the length x is 3√3 ≈ 5.2.
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Additional comment
You can also find the length x using the tangent function:
Tan = Opposite/Adjacent
tan(60°) = x/3
x = 3·tan(60°) = 3√3 ≈ 5.2
The other "special" right triangle is the 45°-45°-90° isosceles right triangle. The side length ratios in that triangle are 1 : 1 : √2.