Question:medium

The general solution of \(cosx+sinx = cos2x+sin2x\) is \(x = npπ\) or \(x = \frac{nqπ}{3}+\frac{π}{6}\) for \(n\in Z\) then \(p:q =\)

Show Hint

Group the equation as cos x - cos 2x = sin 2x - sin x and factor.
Updated On: Oct 1, 2026
  • \(1:1\)
  • \(1:2\)
  • \(2:3\)
  • \(2:1\)
Show Solution

The Correct Option is A

Solution and Explanation

Step 1: Square-free route:
Write each side in the form $\sqrt2\sin(\cdot)$: $\cos x + \sin x = \sqrt2\sin(x + \frac{\pi}{4})$ and $\cos 2x + \sin 2x = \sqrt2\sin(2x + \frac{\pi}{4})$.

Step 2: Equate sines:
$\sin A = \sin B$ gives $A = B + 2n\pi$ or $A = \pi - B + 2n\pi$.
First: $x + \frac\pi4 = 2x + \frac\pi4 + 2n\pi$, so $x = -2n\pi$, that is $x = 2n\pi$.
Second: $x + \frac\pi4 = \pi - 2x - \frac\pi4 + 2n\pi$, so $3x = \frac{\pi}{2} + 2n\pi$, $x = \frac{2n\pi}{3} + \frac{\pi}{6}$.

Step 3: Read p and q:
$p = 2$, $q = 2$, so the ratio is 1:1.

Final Answer:
The ratio p:q is 1:1, option (A). \[ \boxed{1:1} \]
Was this answer helpful?
0