Practicing Success
The function $\frac{\sin (x+\alpha)}{\sin (x+\beta)}$ has no extrema if (n ∈ Z) |
$\alpha-\beta \neq n \pi$ $\beta-\alpha=n \pi$ $\beta-\alpha=2 n \pi$ None of these |
$\alpha-\beta \neq n \pi$ |
$f(x)=\frac{\sin (x+\alpha)}{\sin (x+\beta)}$ $\Rightarrow f'(x)=\frac{\sin (x+\beta) \cos (x+\alpha)-\sin (x+\alpha) \cos (x+\beta)}{\sin ^2(x+\beta)}$ $=\frac{\sin (\beta-\alpha)}{\sin ^2(x+\beta)}$ ∴ f has no extrema if f'(x) ≠ 0 i.e. if sin (β – α) ≠ 0 i.e. if sin (α – β) ≠ 0, i.e. if α – β ≠ nπ, n ∈ Z. |