Show that`cos510^@cos330^@-sin390^@cos120^@=-1/2`

cos1^@+cos2^@+cos3^@+...+cos180^@=

Show that cos24^@+cos55^@+cos125^@+cos204^@+cos300^@=1/2

Prove the following: sin18^@cos39^@+sin6^@cos15^@=sin24^@cos33^@

Show that sin 105^(@) + cos 105^(@) =(1)/(sqrt(2))

The value of sin600^@cos330^@+cos120^@sin150^@ is

Prove the following: cos^2x+cos^2(x+120^@)+cos^2(x-120^@)=3/2

In triangleABC,A+B+C=pi ,show that cos^2A+cos^2B-cos^2C=1-2sinAsinBcosC

The value of sin 600^(@) cos 330^(@)+ cos 120^(@) sin 150^(@) is ............... A) -1 B) 1 C) (1)/(sqrt2) D) (sqrt3)/(2)

If costheta=8/17 and theta lies in the 1^(st) quadrant, then the value of cos(30^@+theta)+cos(45^@-theta)+cos(120^@-theta) is