The value of
$${\cos ^3}\left( {{\pi \over 8}} \right)$$$${\cos}\left( {{3\pi \over 8}} \right)$$+$${\sin ^3}\left( {{\pi \over 8}} \right)$$$${\sin}\left( {{3\pi \over 8}} \right)$$
is :

The equation y = sinx sin (x + 2) – sin² (x + 1) represents a straight line lying in :

The value of sin 10º sin30º sin50º sin70º is :-

The value of cos²10° – cos10°cos50° + cos²50° is