Given:
A prism with height 5 cm and equilateral triangular base with side 2 cm.
To find:
The total surface area of the prism.
Solution:
Area of an equilateral triangle is:

Where, a is the side length.
Putting
, we get




The base and top of the prism are congruent so their area must be equal.
The lateral surface area of the prism is:

Where, P is the perimeter of the base and h is the height of the prism.
The lateral surface area of the prism is:



Now, the total surface area is the sum of areas of bases and lateral surface area.




Therefore, the total surface area is 33.46 cm².
<h3>
Answer: A. 9</h3>
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Explanation:
Draw in the segments AO and OC.
Triangle ABO is congruent to triangle CBO. We can prove this through the use of the HL theorem. HL stands for hypotenuse leg.
Since the triangles are congruent, this means the corresponding pieces AB and BC are the same length.
Then we can say:
AB+BC = AC .... segment addition postulate
AB+AB = AC .... plug in BC = AB
2*AB = AC
2*AB = 18
AB = 18/2 .... divide both sides by 2
AB = 9
In short, the chord AC is bisected by the perpendicular radius drawn in the diagram. So all we do is cut AC = 18 in half to get AB = 9.