For a regular tessellation, the shapes can be duplicated infinitely to fill a plane such that there is no gap. The only shapes that can form regular tessellations are equilateral traingle(all sides are equal. This means that it can be turned to any side and it would remain the same), square and regular hexagon. Looking at the given options, we have
Shape Tessellate?
Octagon No
Hexagon Yes
Pentagon No
Square Yes
Triangle No(unless it is specified that it is an equilateral triangle)
Answer number 3
Step-by-step explanation:
First solve for the trig function 'cot'

Next take the sqrt of both sides (include plus/minus)

Now take reciprocal of both sides, this will change trig function to 'tan'
(cot = 1/tan)

Finally use the unit circle or inverse tan on your calculator to find x.
There will be 4 solutions, one for each quadrant.
If you are looking for the value of N, multiply both sides by 4. The value of N is 4900.