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8. Introduction to Trigonometry
medium
$\tan (65-\theta)-\cot (25-\theta)-\sec (55-\theta)+\operatorname{cosec}(35-\theta)=\ldots \ldots \ldots \ldots . .$ (where, $0 < \theta < 25)$
A
$3$
B
$1$
C
$2$
D
$0$
Solution
$\tan (65+\theta)=\cot [90-(65+\theta)]=\cot (25-\theta)$
and $\operatorname{cosec}(35+\theta)=\sec [90-(35+\theta)]=\sec (55-\theta)$
Now, $\tan (65+\theta)-\cot (25-\theta)-\sec (55-\theta)+\operatorname{cosec}(35+\theta)$
$=\cot (25-\theta)-\cot (25-\theta)-\sec (55-\theta)+\sec (55-\theta)$
$=0$
Standard 10
Mathematics