First slide

Trigonometric equations

Question

If $\cos θ = 1 - 2 t^{2}$ , $0^{\circ} < t < 180^{\circ}$ and $\cos 50^{\circ} = t$ then the value of $θ$ is

Easy

A

$80^{\circ}$
B

$100^{\circ}$
C

$140^{\circ}$
D

$50^{\circ}$

Solution

$\cos θ = 1 - 2 t^{2} = 1 - 2 \cos^{2} 50^{0} = - \cos 100^{0}$
$= \cos (180^{0} - 100^{0}) = \cos 80^{0}$
$∴ θ = 80^{0}$

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