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WBJEE · Maths · Trigonometric Equations

Let \(\alpha\) and \(\beta\) be iwo distinct roots of \(a \cos \theta+b \sin \theta=c,\) where \(a, b, c\) are three
real constants and \(0 \in|0,2 \pi|\). Then, \(\alpha+\beta\) is also a root of the same equation, if

  1. A \(a+b=c\)
  2. B \(b+c=a\)
  3. C \(c+a=b\)
  4. D \(c=a\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(c=a\)

Step-by-step Solution

Detailed explanation

Given equation is \(a \cos \theta+b \sin \theta=c\) \(\Rightarrow a\left(\frac{1-\tan ^{2} \frac{\theta}{2}}{1+\tan ^{2} \frac{\theta}{2}}\right)+\frac{2 b \tan \frac{\theta}{2}}{1+\tan ^{2} \frac{\theta}{2}}=c\)…