📚 CBSE Grade-10 Study Guide Open in the Study Guide single page app →
HomeMathematics

Mathematics — CBSE Class 10 board question

Q1. [2]
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, open the Study Guide single page app, go to Library and find the actual CBSE question paper. The original papers are also available 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.