cos θ/1−tan θ + sin θ/1−cot θ = ……… A) cos θ – sin θ B) tan θ – cot θ C) cos θ – sin θ D) tan θ + cot θ
cos θ/1−tan θ + sin θ/1−cot θ = ………
A) cos θ – sin θ
B) tan θ – cot θ
C) cos θ – sin θ
D) tan θ + cot θ
2 Answers
Correct option is: C) cos \(\theta\) + sin \(\theta\)
\(\frac{cos\theta}{1-tan\theta} + \frac{sin\theta}{1-cot\theta}\)= \(\frac {cos\theta}{\frac {1-sin\theta}{cos\theta}} + \frac {sin\theta}{\frac {1-cos\theta}{sin\theta}}\)
= \(\frac {cos^2\theta}{cos\theta - sin \theta} + \frac {sin^2\theta}{sin\theta - cos\theta}\)
= \(\frac {cos^2\theta}{cos\theta - sin \theta} - \frac {sin^2\theta}{sin\theta - cos\theta}\)
= \(\frac {cos^2\theta - sin^2\theta}{cos\theta - sin \theta}\)
= \(\frac {(cos\theta - sin \theta) (cos\theta + sin \theta)}{cos\theta - sin\theta}\)
= cos \(\theta\) + sin \(\theta\)