CBSE · Class 10 · Mathematics · Introduction to TrigonometryWhat is the value of $\frac{\sin 18^\circ}{\cos 72^\circ}$?
Step-by-Step Solution
We know the complementary angle relation: $\cos(90^\circ - \theta) = \sin \theta$. Therefore, $\cos 72^\circ = \cos(90^\circ - 18^\circ) = \sin 18^\circ$. Substituting this into the given expression: $\frac{\sin 18^\circ}{\sin 18^\circ} = 1$.
Detailed Options Breakdown
Option : 0
Incorrect choice. This distractor represents a common misunderstanding of the core principles of Introduction to Trigonometry.
Option 1: 1 (Correct Answer)
Correct choice. Refer to the step-by-step verified solution guidelines above for details.
Option 2: 18
Incorrect choice. This distractor represents a common misunderstanding of the core principles of Introduction to Trigonometry.
Option 3: 72
Incorrect choice. This distractor represents a common misunderstanding of the core principles of Introduction to Trigonometry.
💡 Study Guide: This question tests core syllabus concepts from Introduction to Trigonometry. For formulas, key summaries, and mock exam reference guides, read the full Introduction to Trigonometry Revision Notes.