[" 33"cos4 theta-cos4 alpha],[=8(cos theta-cos alpha)(cos theta+cos alpha)(cos theta-sin alpha)]

Prove that cos 4theta–cos 4alpha = 8(cos theta-cos alpha)(cos theta+ cos alpha )(cos theta -sin alpha)(cos theta+sin alpha)

cos ( theta + alpha)* cos ( theta - alpha) + sin ( theta + alpha) * sin (theta - alpha )=

If tan alpha=(sin theta-cos theta)/(sin theta+cos theta) then sin alpha

if sin(theta+alpha)=cos(theta+alpha) then tan alpha

Simplify be reducing to a single term : cos (theta + alpha ) cos ( theta - alpha ) - sin ( theta + alpha ) sin (theta - alpha).

Show that: cos^(2)theta+cos^(2)(alpha+theta)-2cos alpha cos theta cos(alpha+theta) is independent of theta.

tan theta = (sin alpha-cos alpha) / (sin alpha + cos alpha)

If cos (theta - alpha) , cos theta , cos (theta + alpha ) are in H.P. then cos theta .sec"" (alpha )/(2) =

Prove that cos^(2)theta + cos^(2)(alpha + theta) – 2cos alpha *cos theta* cos(alpha +theta) is independent of theta .