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Statement-1: (cos36^(@)-cos752^(@))/(co...

Statement-1: `(cos36^(@)-cos752^(@))/(cos36^(@)cos72^(@))=2`
Statement-2: `sin15^(@)=(sqrt6-sqrt7)/(4)`

A

Statement-1 is True, Statement-2 is true, Statement-2 is a correct explanation for Statement -1.

B

Statement-1 is True, Statement-2 is True, Statement-2 is not a correct explanation for Statement-1.

C

Statement-1 is True, Statement-2 is False.

D

Statement-1 is False, Statement-2 is True.

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze both statements and prove or disprove them step by step. ### Statement 1: We need to prove that: \[ \frac{\cos 36^\circ - \cos 72^\circ}{\cos 36^\circ \cos 72^\circ} = 2 \] **Step 1: Rewrite \(\cos 72^\circ\)** Using the identity \(\cos(90^\circ - \theta) = \sin \theta\), we can rewrite \(\cos 72^\circ\): \[ \cos 72^\circ = \sin 18^\circ \] **Step 2: Substitute into the equation** Substituting this into our equation gives: \[ \frac{\cos 36^\circ - \sin 18^\circ}{\cos 36^\circ \sin 18^\circ} \] **Step 3: Use known values of \(\cos 36^\circ\) and \(\sin 18^\circ\)** We know: \[ \cos 36^\circ = \frac{\sqrt{5} + 1}{4}, \quad \sin 18^\circ = \frac{\sqrt{5} - 1}{4} \] Substituting these values in: \[ \frac{\frac{\sqrt{5} + 1}{4} - \frac{\sqrt{5} - 1}{4}}{\frac{\sqrt{5} + 1}{4} \cdot \frac{\sqrt{5} - 1}{4}} \] **Step 4: Simplify the numerator** The numerator simplifies to: \[ \frac{\left(\sqrt{5} + 1 - (\sqrt{5} - 1)\right)}{4} = \frac{2}{4} = \frac{1}{2} \] **Step 5: Simplify the denominator** The denominator simplifies to: \[ \frac{(\sqrt{5} + 1)(\sqrt{5} - 1)}{16} = \frac{5 - 1}{16} = \frac{4}{16} = \frac{1}{4} \] **Step 6: Combine the results** Now, substituting back into the equation: \[ \frac{\frac{1}{2}}{\frac{1}{4}} = \frac{1}{2} \cdot 4 = 2 \] Thus, Statement 1 is **true**. ### Statement 2: We need to verify if: \[ \sin 15^\circ = \frac{\sqrt{6} - \sqrt{7}}{4} \] **Step 1: Use the sine subtraction formula** Using the formula \(\sin(a - b) = \sin a \cos b - \cos a \sin b\): \[ \sin 15^\circ = \sin(45^\circ - 30^\circ) = \sin 45^\circ \cos 30^\circ - \cos 45^\circ \sin 30^\circ \] **Step 2: Substitute known values** Substituting the known values: \[ \sin 45^\circ = \frac{1}{\sqrt{2}}, \quad \cos 30^\circ = \frac{\sqrt{3}}{2}, \quad \cos 45^\circ = \frac{1}{\sqrt{2}}, \quad \sin 30^\circ = \frac{1}{2} \] Thus, we have: \[ \sin 15^\circ = \frac{1}{\sqrt{2}} \cdot \frac{\sqrt{3}}{2} - \frac{1}{\sqrt{2}} \cdot \frac{1}{2} \] **Step 3: Simplify** This simplifies to: \[ \sin 15^\circ = \frac{\sqrt{3}}{2\sqrt{2}} - \frac{1}{2\sqrt{2}} = \frac{\sqrt{3} - 1}{2\sqrt{2}} \] **Step 4: Rationalize the denominator** To rationalize: \[ \sin 15^\circ = \frac{\sqrt{3} - 1}{2\sqrt{2}} \cdot \frac{\sqrt{2}}{\sqrt{2}} = \frac{\sqrt{6} - \sqrt{2}}{4} \] Since \(\frac{\sqrt{6} - \sqrt{2}}{4} \neq \frac{\sqrt{6} - \sqrt{7}}{4}\), Statement 2 is **false**. ### Conclusion: - Statement 1 is **true**. - Statement 2 is **false**.

To solve the problem, we need to analyze both statements and prove or disprove them step by step. ### Statement 1: We need to prove that: \[ \frac{\cos 36^\circ - \cos 72^\circ}{\cos 36^\circ \cos 72^\circ} = 2 \] ...
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