First slide

Multiple and sub- multiple Angles

Question

If $\tan \frac{α}{2}, \tan \frac{β}{2}$ are the roots of $8 x^{2} - 26 x + 15 = 0$ then $\cos (α + β) =$

Moderate

A

$\frac{627}{725}$
B

$\frac{547}{715}$
C

$\frac{- 547}{715}$
D

$\frac{- 627}{715}$

Solution

$\tan \frac{(α + β)}{2} = \frac{26 / 8}{1 - 15 / 8} = - \frac{26}{7}$
$\Rightarrow \cos (α + β) = - \frac{627}{725}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App