Prove that `(4cos^2 9^0-3)(4cos^2 27^0-3)=tan9^0dot`

Prove that (2cos2A+1)/(2cos2A-1)=tan(60^0+A)tan(60^0-A)

Prove that, cos80^(@)+cos40^(@)-cos20^(@)=0

Prove that (sin5x+sin3x)/(cos5x+cos3x)=tan4x

Prove that, cos55^(@)+cos65^(@)+cos175^(@)=0

Prove that : sin^(2)((pi)/(6))+cos^(2)((pi)/(3))-tan^(2)((pi)/(4))=-(1)/(2)

The values of cos^2 73^0+cos^2 47^0-sin^2 43^0+sin^2 107^0 is equal to: (a) 1 (b) 1/2 (c) (sqrt(3))/2 (d) sin^2 73^@+cos^4 73^@

4\ cos\ 20^0\ -sqrt(3)\ cot\ 20^0\ =

Prove that, cos^(2)45^(@)-sin^(2)15^(@)=sqrt(3)/(4)

Prove that cos((3pi)/(4)+x)-cos((3pi)/(4)-x)=-sqrt(2)sinx