Take the length of one of the sides and times that by the radius. Divide that answer by 2. Now take that and multiply by the number of sides the polygon has. If you can't find the radius or side, you're going to have to use tan, sin, or cos.
The formula you need to use is C = 5/9•(F - 32)
So take 15 and subtract 32: 15-32 = -17
Then multiply that by 5/9: 5/9•(-17) ≈ -9.44
The value of the trigonometric ratio, Cos C is 5/13. The answer is A.
2√72 / √8 ± √2
If the denominator is √8 + √2,
2√72 / √8 + √2
= 2√(2*2*2*3*3) / √(2*2*2) + √2
= 2*2*3√2 / 2√2 + √2
= 12√2 / 3√2
= 4
