Question

please solve 9th question

Answer 1

$\pink {\huge{\underline{\star\: Solution\: \star}}}$

$\frak{Hey \: Mate\: !}$

$cos A = \sqrt{\frac{1+cos2A}{2}}\\ \implies Let\: A = 30\degree \\ cos 30\degree = \sqrt{\frac{1+cos2(30\degree}{2}}\\ cos 30\degree = \sqrt{\frac{1+cos60\degree}{2}}\\ cos 30\degree = \sqrt{\frac{1+\frac{1}{2}}{2}}\\ cos 30\degree= \sqrt{\frac{\frac{2+1}{2}}{2}}\\\cos30\degree=\sqrt{\frac{3}{4}}\\\implies cos 30\degree= \frac{\sqrt{3}}{2}$

$\red{\underline{Answer}}$

$\pink{\boxed{\implies cos 30\degree= \frac{\sqrt3}{2}}}$

Answer 2

Hello!

• A = $\bf{30^{\circ}}$

Then,

$\underline{\bf{cos\: 30^{\circ}}}$ :

$\sqrt{} \dfrac{1 + \sf 2cos\: 30^{\circ}}{2}$

⇒ $\sqrt{} \dfrac{1 + \sf cos \:60^{\circ}}{2}$

⇒ $\sqrt{} \dfrac{1 + \dfrac{1}{2}}{2}$

⇒ $\sqrt{} \dfrac{3}{4}$ ⇒ $\boxed{\blue{\bf{\dfrac{\sqrt{3}}{2}}}}$

Cheers!