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Question

If $\sin \theta - \cos \theta = 0$, and $0 \le \theta \le 90^\circ$, then the value of $\sin \theta + \cos \theta$ is:

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
$\sqrt{2}$

Trigonometric Equation Analysis

We are given the equation $\sin \theta - \cos \theta = 0$, with the constraint that $0 \le \theta \le 90^\circ$.

Solving for Angle Theta

  1. From $\sin \theta - \cos \theta = 0$, we get $\sin \theta = \cos \theta$.
  2. Assuming $\cos \theta \neq 0$, we can divide both sides by $\cos \theta$ to get $\frac{\sin \theta}{\cos \theta} = 1$, which means $\tan \theta = 1$.
  3. Considering the range $0 \le \theta \le 90^\circ$, the angle $\theta$ for which $\tan \theta = 1$ is $\theta = 45^\circ$.

Calculating Sin θ + Cos θ

Now, we need to find the value of $\sin \theta + \cos \theta$ when $\theta = 45^\circ$.

  1. Substitute $\theta = 45^\circ$ into the expression: $\sin 45^\circ + \cos 45^\circ$.
  2. We know that $\sin 45^\circ = \frac{1}{\sqrt{2}}$ and $\cos 45^\circ = \frac{1}{\sqrt{2}}$.
  3. Therefore, $\sin 45^\circ + \cos 45^\circ = \frac{1}{\sqrt{2}} + \frac{1}{\sqrt{2}}$.
  4. Adding these values gives $\frac{2}{\sqrt{2}}$.
  5. Simplifying $\frac{2}{\sqrt{2}}$ by multiplying the numerator and denominator by $\sqrt{2}$ yields $\frac{2\sqrt{2}}{2}$, which simplifies to $\sqrt{2}$.

Thus, the value of $\sin \theta + \cos \theta$ is $\sqrt{2}$.

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Similar Questions

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Important Questions from Trigonometric Ratios and Identities

  1. If cosec θ = 13/12, then sin θ + cos θ - tan θ is equal to:

  2. What is the value of \(\frac{3 \sin 58^{\circ}}{\cos 32^{\circ}}+\frac{3 \sin 42^{\circ}}{\cos 48^{\circ}}\) ?

  3. If \(\frac{{\tan \theta + \sin \theta }}{{\tan \theta - \sin \theta }} = \frac{{k + 1}}{{k - 1}},\) then k = ?

  4. If α + β = 90° and α = 2β, then the value of 3 cos 2 α - 2 sin 2 β is equal to:

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