-π/2 < arctan(x) < π/2
So cos(π/2) < cos(arctan(x)) < cos(0)
0 < cos(arctan(x)) < 1
When a line and a curve are tangent to each other, they are joined together by 1 point (x,y). So, you equate both equations either in terms of x or y. For this problem, let's equate in terms of y.
y = k - x
y = x² + 3x + 1
k - x = x² + 3x + 1
k = x² + 3x + x + 1
k = x² + 4x + 1
This would be the value of k. Since we are not given the common point, it can only be expressed in terms of x or y.
216/ 120 times 90 divided by 18 times 5 and the answer is 45
The interquartile range is A. 15.5
