Question:

If $f: R \rightarrow S $ defined by $ f(x)=\sin x-\sqrt{3} \,\cos\,x+\,$ 1, is onto, function then S = ?

Updated On: Jul 5, 2022
  • [0, 3]
  • [-1, 1]
  • [0, 1]
  • [-1, 3]
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The Correct Option is D

Solution and Explanation

Since $- 2 \leq \,\sin \,x -\sqrt{3} \,\cos\, x\, \leq\, 2$ $\therefore -1 < \sin x - \sqrt{3} \cos\, x \,+ 1 \leq 3$ $\therefore R_f = [-1, 3]$ $\therefore$ [-1, 3] holds . $\begin{Bmatrix} \because \sin \, x - \sqrt{3} \,\cos \, x \\[0.3em] = 2\left[\frac{1}{2}\sin \, x= \frac{\sqrt 3}{2}\cos \, x\right] \\[0.3em] = 2\left[\sin\left(x- \frac{\pi}{6} \right)\right] \end{Bmatrix}$
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Concepts Used:

Relations and functions

A relation R from a non-empty set B is a subset of the cartesian product A × B. The subset is derived by describing a relationship between the first element and the second element of the ordered pairs in A × B.

A relation f from a set A to a set B is said to be a function if every element of set A has one and only one image in set B. In other words, no two distinct elements of B have the same pre-image.

Representation of Relation and Function

Relations and functions can be represented in different forms such as arrow representation, algebraic form, set-builder form, graphically, roster form, and tabular form. Define a function f: A = {1, 2, 3} → B = {1, 4, 9} such that f(1) = 1, f(2) = 4, f(3) = 9. Now, represent this function in different forms.

  1. Set-builder form - {(x, y): f(x) = y2, x ∈ A, y ∈ B}
  2. Roster form - {(1, 1), (2, 4), (3, 9)}
  3. Arrow Representation