C = 2πr Divide both sides by 2π
C/2π = r Switch the sides to make it easier to read
r = c / 2π
Given:
In 2010, the population of a town = 2000
Every year, it increase by 1.5%
To find the equation P(t) which represents the population of this town t years from 2010.
Formula
If a be the original population of a town and it increases by b% every year, after t year the population will be

Now,
Taking, a =2000, b = 1.5 we get,

or, 
Hence,
The population of this town t years from 2010 P(t) =
, Option D.
X = 42 - 19, so A - x = 23
1. Given any triangle ABC with sides BC=a, AC=b and AB=c, the following are true :
i) the larger the angle, the larger the side in front of it, and the other way around as well. (Sine Law) Let a=20 in, then the largest angle is angle A.
ii) Given the measures of the sides of a triangle. Then the cosines of any of the angles can be found by the following formula:

2.

3. m(A) = Arccos(-0.641)≈130°,
4. Remark: We calculate Arccos with a scientific calculator or computer software unless it is one of the well known values, ex Arccos(0.5)=60°, Arccos(-0.5)=120° etc