Question

if cos^2 thetha - sin^2 thetha =3/4 than cos thetha is ? ​

Answer 1

Answer:

$\cos( \alpha ) = \frac{ \sqrt{7} }{2 \sqrt{2} } .$

Step-by-step explanation:

${ \cos( \alpha ) }^{2} - { \sin( \alpha ) }^{2} = \frac{3}{4} \\ \\ { \cos( \alpha ) }^{2} - (1 - { \cos( \alpha ) }^{2} ) = \frac{3}{4} \\ \\ 2 { \cos( \alpha ) }^{2} - 1 = \frac{3}{4} \\ \\ 2 { \cos( \alpha ) }^{2} = \frac{7}{4} \\ \\ { \cos( \alpha ) }^{2} = \frac{7}{8} \\ \\ \cos( \alpha ) = \frac{ \sqrt{7} }{2 \sqrt{2} } .$