If θ is an acute angle and 7 + 4θ = 9, then the value of θ is : (A) 90° (B) 30° (C) 45° (D) 60°

MathsCBSE Class 10 · Standard · Board exam 2025, set 30/1/1 · 1 mark · MCQ

CBSE Class 10 Mathematics Standard 2025: question 4

Set in the CBSE Class 10 board exam of 2025, paper 30/1/1, section A, question 4, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q4 · 1 mark · MCQIntroduction to Trigonometry

If $θ$ is an acute angle and $7 + 4 sin θ = 9$ , then the value of $θ$ is :

(A) $9 0^{\circ}$
(B) $3 0^{\circ}$
(C) $4 5^{\circ}$
(D) $6 0^{\circ}$

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 30/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Make $sin θ$ the subject of the equation.

Hint 2

Which standard angle has a sine of $1/2$ ?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

From $7 + 4 sin θ = 9$ we get $4 sin θ = 2$ , so $sin θ = \frac{1}{2}$ .
$sin 3 0^{\circ} = \frac{1}{2}$ and $θ$ is acute, so $θ = 3 0^{\circ}$ . This is option (B).
1 mark

Answer: θ = 30°, option (B)

Where the marks are

Gets $sin θ = 1/2$ and hence $θ = 3 0^{\circ}$ , option (B) (1 mark)

Revise the chapter

Chapter: Introduction to Trigonometry (notes, formulas, where marks are lost and every past question)

Practise this chapterBoard-style questions from Introduction to Trigonometry, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 30/1/1 (Standard): every question, by section.

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CBSE Class 10 Mathematics Standard 2025: question 4

Hints

Step-by-step solution

Revise the chapter

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