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Question
`(cos 25^circ + sin 25^circ)/(cos 25^circ - sin 25^circ)` = ?
Options
tan 25°
cot 20°
tan 65°
cot 35°
MCQ
Solution
cot 20°
Explanation:
`(cos 25^circ + sin 25^circ)/(cos 25^circ - sin 25^circ) = (1 + tan 25^circ)/(1 - tan 25^circ)`
`= (tan 45^circ + tan 25^circ)/(1 - tan 45^circ tan 25^circ)`
= tan (45° + 25°)
= tan 70°
tan (90° - 20°)
= cot 20°
shaalaa.com
Trigonometric Functions of Sum and Difference of Angles
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