The function is defined as $y = [x]$, where $[x]$ represents the greatest integer less than or equal to $x$. The task is to find the area under this curve for the interval $x \in [1, 4]$.
The interval $[1, 4]$ can be divided into subintervals where the value of $[x]$ remains constant:
The total area under the curve $y = [x]$ from $x=1$ to $x=4$ is the sum of the areas calculated for each subinterval. This can be represented as the definite integral:
$ \text{Total Area} = \int_{1}^{4} [x] \, dx = \int_{1}^{2} 1 \, dx + \int_{2}^{3} 2 \, dx + \int_{3}^{4} 3 \, dx $
Summing the individual areas:
$ \text{Total Area} = 1 + 2 + 3 = 6 $
Therefore, the area under $y = [x]$ for $x \in [1, 4]$ is 6 square units.
The work done by the force $F = (x + y)\hat{i} - (x^2 + y^2)\hat{j}$, where $\hat{i}$ and $\hat{j}$ are unit vectors in $\vec{OX}$ and $\vec{OY}$ directions, respectively, along the upper half of the circle $x^2 + y^2 = 1$ from $(1,0)$ to $(-1,0)$ in the $xy$-plane is

In the figure shown above, PQRS is a square. The shaded portion is formed by the intersection of sectors of circles with radius equal to the side of the square and centers at S and Q.
The probability that any point picked randomly within the square falls in the shaded area is ___________.