[" 12.Prove that "],[qquad cos510^(@)cos330^(@)+sin390^(@)cos120^(@)=-1]

Prove that, cos510^(@)cos330^(@)+sin390^(@)cos120^(@)=-1 .

cos 510^@cos330^@+sin 390^@cos120^@ =

Prove that cos510^@cos330^@+sin390^@cos120^@=-1

Prove that: cos510^(0)cos330^(@)+s in390^(@)cos120^(@)=-1

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

Prove that: cos570^(@)s in510^(0)+sin(-330^(@))cos(-390^(@))=0

sin150^(@).cos120^(@)+cos330^(@)*sin660^(@)=-1

Prove that: (a) cos510^(@) sin510^(@) + sin(-330^(@)) cos(-390^(@))=0 b) tan(11pi)/(3) -2sin(9pi)/3-3/4"cosec"^(2)pi/4 + 4cos^(2)(17pi)/6=(3-2sqrt(3))/2

Prove that: (a) cos510^(@) sin510^(@) + sin(-330^(@)) cos(-390^(@))=0 b) tan(11pi)/(3) -2sin(9pi)/3-3/4"cosec"^(2)pi/4 + 4cos^(2)(17pi)/6=(3-2sqrt(3))/2

sin120^(@)cos150^(@)-cos240^(@)sin330^(@)=