(cos2A)/(a^(2))-(cos28)/(6^(2))=

Prove that ((sin^(2)73^(@)+sin^(2)17^(@)))/((cos^(2)28^(@)+cos^(2)62^(@)))=1.

(1+cos 56^(@)+cos58^(@)-cos66^(@))/(cos28^(@)cos29^(@)sin33^(@))=kcos(A/2)cos(B/2)sin(c/2) then k=?

Evaluate 2(cos^(2)28^(@)-sin^(2)62^(@)) .

Evaluate 2(cos^(2)28^(@)-sin^(2)62^(@)) .

The number of solutions of the equation cos^(2)(x+(pi)/(6))+cos^(2)x-2cos(x+(pi)/(6))*cos(pi)/(6)=sin^(2)(pi)/(6) in interval ((-pi)/(2),(pi)/(2)) is

Prove that : cos^(2)A+cos^(2)(A+pi/3)+cos^(2)(A-pi/3) =1/2[2cos^(2)A+2cos^(2)(A+60^(@))+2cos^(2)(A-60^(@))] =1/2[1+cos2A+1+cos(2A+120^(@))+1+cos(2A-120^(@))] 1/2[3+cos2A+cos(2A+120^(@))+cos(2A-120^(@))] 1/2[3+cos2A+2cos(2A+120^(@)+2A-120^(@))/(2).cos(2A+120^(@)-2A+120^(@))/(2)] =1/2[3+cos2A+2cos2Acos120^(@)] =1/2[3cos2A+2cos2Acos(90^(@)+30^(@))] =1/2[3+cos2A-2.cos2A.(1/2)] =1/2(3+cos2A-cos2A) =3/2 = RHS Hence Proved.

In Delta ABC prove that cos ec(A)/(2)cos ec(B)/(2)cos ec(C)/(2)>=6

The exact value of cos((2 pi)/(28))cos ec((3 pi)/(28))+cos((6 pi)/(28))cos ec((9 pi)/(28))+cos((18 pi)/(28))cos ec((27 pi)/(28))