The answer is (C). All sides and angles of the square is equal. Its diagonals bisect each other and meet at 90°. If two lines are said to meet at 90°, these lines are perpendicular to each other. Therefore, the diagonals of a square is perpendicular to each other
Here the given expression is

We need to find the value of y when x =3 . So we substitute the value of x in the given expression.

So when x=3, y=0.4 and that's the required answer.