Mark the Correct alternative in the following:

The value of cos 52^o + cos 68^o + cos 172^o is

Mark the Correct alternative in the following:

sin 163^o cos 347^o + sin 73^o sin 167^o =

Mark the Correct alternative in the following:

If and then

Mark the Correct alternative in the following:

The value of sin 78^o – sin 66^o – sin 42^o + sin 6^o is

Mark the Correct alternative in the following:

If sin α + sin β = a and cos α – cos β = b, then