The numerator is 5 (and the denominator is 10).
Looking at the angles of the triangles
N=S
M=R
O=T
so MON would be RTS
Answer : 6 is opposite of 1
The question is related to trigonometry and we have to use the formula of double angle .
Here we use double angle formula of tangent function which is

Given expression is

Comparing it with double angle formula, we will get x = 5
SO the required expression is equal to


So the answer is tan(10) .