Can you give the data please?
This would be a great question to just plug into a calculator. I'm sure you will find the answer quite easily if you use a calculator.
There are 108° in each interior angle of<span> a </span><span>regular pentagon.</span>
We have that
<span>y=2sinx-cosx
y=cosx
</span>over the interval 0≤x≤pi/2-------> 0≤x≤1.57
using a graph tool
see the attached figure
the solution in the given interval is the point (pi/4, 0.707)
the y-value of the point of intersection is 0.707 -----> √2/2
the answer is the option <span>
b. (square root of 2)/2</span>