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8. Introduction to Trigonometry
medium
If $A+B+C=180,$ then $\tan \left(\frac{A+B}{2}\right)=$ ...........
A
$\cot \left(\frac{A+B}{2}\right)$
B
$\cot \frac{ C }{2}$
C
$\sec \frac{ C }{2}$
D
$\sin \frac{A}{2}$
Solution
$A+B+C=180 \quad \therefore A+B=180-C \quad \therefore \frac{A+B}{2}=90-\frac{C}{2}$
$\therefore \tan \left(\frac{A+B}{2}\right)=\tan \left(90-\frac{C}{2}\right)=\cot \frac{C}{2}$
Standard 10
Mathematics