Find the value of `cos1140^@`

Find the values of: cos315^@

Find the values of: cos600^@

Find the value of cos 12^(@)+cos 84^(@)+cos 156^(@)+cos 132^(@)

Find the value of cos 60^@ xx cos 30^@+sin 60^@ xx sin 30^@ .

Find the value of cos 60^@ xx cos 30^@ + sin 60^@ xx sin 30^@

Find the values of: cos75^@

The value of cos105^@ is

If theta lies in the first quardrant and costheta=(8)/( 17 ) , then find the value of cos(30^(@)+theta)+cos(45^(@)-theta)+cos(120^(@)-theta) .