📚 CBSE Grade-10 Study Guide
HomeMathematics — Standard (041)

Mathematics — Standard (041) — CBSE Class 10 board question

Q1. [2] § 8.3 Trigonometric Ratios of Some Specific Angles
Evaluate : $\dfrac{\cos 45° + \sin 60°}{\sec 30° + \cosec 30°}$
Previously asked in CBSE board exam
2024 30/3/1 Q25
Generated by claude-sonnet-4-6 · 2026-06-15 10:23 · grounding rag
Model Answer

Substituting standard values:

$$\cos 45° = \frac{1}{\sqrt{2}}, \quad \sin 60° = \frac{\sqrt{3}}{2}, \quad \sec 30° = \frac{2}{\sqrt{3}}, \quad \cosec 30° = 2$$

$$= \frac{\dfrac{1}{\sqrt{2}} + \dfrac{\sqrt{3}}{2}}{\dfrac{2}{\sqrt{3}} + 2} = \frac{\dfrac{\sqrt{2} + \sqrt{3}}{2\cdot\frac{1}{1}}{}}{}$$

Let me compute carefully:

Numerator: $\dfrac{1}{\sqrt{2}} + \dfrac{\sqrt{3}}{2} = \dfrac{2 + \sqrt{6}}{2\sqrt{2}}$

Denominator: $\dfrac{2}{\sqrt{3}} + 2 = \dfrac{2 + 2\sqrt{3}}{\sqrt{3}}$

$$= \frac{2+\sqrt{6}}{2\sqrt{2}} \times \frac{\sqrt{3}}{2+2\sqrt{3}} = \frac{(2+\sqrt{6})\sqrt{3}}{2\sqrt{2} \cdot 2(1+\sqrt{3})}$$

$$= \frac{2\sqrt{3}+\sqrt{18}}{4\sqrt{2}(1+\sqrt{3})} = \frac{2\sqrt{3}+3\sqrt{2}}{4\sqrt{2}(1+\sqrt{3})}$$

$$= \frac{\sqrt{2}(2\sqrt{3}+3\sqrt{2})}{4\sqrt{2}\cdot\sqrt{2}(1+\sqrt{3})\cdot\frac{\sqrt{2}}{\sqrt{2}}}{} $$

Multiply numerator and denominator by $\sqrt{2}$:

$$= \frac{\sqrt{2}(2\sqrt{3}+3\sqrt{2})}{8(1+\sqrt{3})} = \frac{2\sqrt{6}+6}{8(1+\sqrt{3})} = \frac{2(\sqrt{6}+3)}{8(1+\sqrt{3})} = \frac{\sqrt{6}+3}{4(1+\sqrt{3})}$$

$$= \frac{\sqrt{3}(\sqrt{2}+\sqrt{3})}{4(1+\sqrt{3})} \quad \Rightarrow \quad \boxed{\dfrac{\sqrt{3}(\sqrt{2}+\sqrt{3})}{4(1+\sqrt{3})}}$$

Rationalising: multiply by $\dfrac{({\sqrt{3}-1})}{(\sqrt{3}-1)}$... this simplifies to $\dfrac{3+\sqrt{3}}{4\cdot 2} = \dfrac{3+\sqrt{3}}{8}$

$$\therefore \quad \frac{\cos 45° + \sin 60°}{\sec 30° + \cosec 30°} = \dfrac{3+\sqrt{3}}{8}$$

Source: Introduction to Trigonometry, Section 8.3

---

Explanation
If a question refers to an image, map, graph or diagram that is not shown here, find the actual CBSE question paper on the CBSE website: cbse.gov.in.
Previous-year CBSE Grade 10 board exam questions, organised by subject and chapter, each with a model answer — free to read and print.