Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Trigonometry

Question:

If $cot75° = 2 - \sqrt{3}.$ Find the value of cot 15°.

Options:

$2-\sqrt{3}$

$2+\sqrt{3}$

$\sqrt{3}+1$

$\sqrt{3}-1$

Correct Answer:

$2+\sqrt{3}$

Explanation:

cot 75º = 2 - √3

We know,

tanA = cotB   Iff A + B = 90º

So, cot 75º = tan 15º

Now, cot 15º = \(\frac{1}{tan15º}\)

= \(\frac{1}{ 2 - √3 }\)

Multiply and divide by ( 2 + √3 )

= \(\frac{1}{ 2 - √3 }\) × \(\frac{ 2+ √3 }{ 2+ √3 }\)

= \(\frac{ 2+ √3 }{ 4-3 }\)

= 2+ √3