Find the value of
`cos^(2)1^@+cos^(2)2^@+............cos^(2)180^@`

Find the value of cos^-1(-1//2) .

Find the value of (1-cos^(2)A)*"cosec"^(2)A .

The value of cos1^(@) cos 2^(@) ..............cos179^(@) is

Find the value of cos^(2)1^(@)+cos^(2)2^(@)+cos^(2)3^(@)+ -----+cos^(2)87^(@)+cos^(2)88^(@)+cos^(2)89^(@)+cos^(2)90^(@)

Find the value of (4cos^(2)9^(@)-1)(4cos^(2)27^(@)-1) (4cos^(2)81^(@)-1)(4cos^(2)243^(@)-1) .

Find the value of (1+cos A)(1-cos A)cosec^(2)A .

Find the principal value of cos^(-1)(1/2) .

What is the value of cos1^(@) cos2^(@)cos3^(@).....cos270^(@) ?

Find the value of ((cos1^(@)+sin1^(@))(cos2^(@)+sin2^(@))(cos3^(@)+sin3^(@))...(cos 45^@sin45^@))/( cos1^(@)cos2^(@)cos3^(@)...cos45^(@))