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Question

If \(\sin x + \cos x = \sqrt{2}\), what is the value of \(\sin x - \cos x\)?

This question was previously asked in
SSC CGL 2025 Tier 2 Paper 1 Question Paper (19-Jan-2026)
The correct answer is

0

Square both sides of \(\sin x + \cos x = \sqrt{2}\):

\((\sin x + \cos x)^2 = 2\)

\(\sin^2 x + 2\sin x\cos x + \cos^2 x = 2\)

Use \(\sin^2 x + \cos^2 x = 1\):

\(1 + 2\sin x\cos x = 2 \;\Longrightarrow\; 2\sin x\cos x = 1 \;\Longrightarrow\; \sin 2x = 1\)

So \(2x = 90^\circ \;\Longrightarrow\; x = 45^\circ\).

At \(x = 45^\circ\): \(\sin x = \cos x = \dfrac{1}{\sqrt{2}}\), so

\(\sin x - \cos x = \dfrac{1}{\sqrt{2}} - \dfrac{1}{\sqrt{2}} = 0\)

Hence the answer is 0 — option (1).

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