Question

If sec theta = - √30 / 3, find cos theta. if sin(-theta) = -0.97, find cos (π/2 - theta).

Answer 1

Step-by-step explanation:

$\cos \theta = \frac{1}{ \sec\theta } = - \frac{3}{ \sqrt{30} } = - \frac{3 \sqrt{30} }{30} = - \frac{ \sqrt{30} }{10}$

$\cos( \frac{\pi}{2} - \theta )= \cos \frac{\pi}{2} \cos \theta + \sin \frac{\pi}{2} \sin \theta$

Note that

$\sin( - \theta) = - \sin \theta$

$\cos \frac{\pi}{2} = 0 \: \: \: \: \: \sin \frac{\pi}{2} = 1$

Therefore,

$\cos( \frac{\pi}{2} - \theta ) = 0.97$