cos2A=

Prove the following tan^2A- tan^ 2B=(sin^2A-sin^2B)/(cos^2A*cos^2B) =(cos^2B-cos^2A) /(cos^2A*cos^2B)

Show that cos 2A=cos^(2)A-sin^(2)A

Prove that: cos^2A+cos^2(A+(2pi)/3)+cos^2(A-(2pi)/3)=3/2

In A B C Prove that cos^2A/2+cos^2B/2+cos^2C/2lt=9/4dot In cos^2A/2+cos^2B/2+cos^2C/2=y(x^2+1/(x^2)) then find the maximum value of ydot

In A B C Prove that cos^2A/2+cos^2B/2+cos^2C/2lt=9/4dot If cos^2A/2+cos^2B/2+cos^2C/2=y(x^2+1/(x^2)) then find the maximum value of ydot

In A B C Prove that cos^2A/2+cos^2B/2+cos^2C/2lt=9/4dot In cos^2A/2+cos^2B/2+cos^2C/2=y(x^2+1/(x^2)) then find the maximum value of ydot

In A B C Prove that cos^2A/2+cos^2B/2+cos^2C/2lt=9/4dot If cos^2A/2+cos^2B/2+cos^2C/2=y(x^2+1/(x^2)) then find the maximum value of ydot

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.

The value of cos^2 5^@ + cos^2 10^@ + cos^2 15^@ + cos^2 20^@+ cos^2 70^@ + cos^2 75^@+ cos^2 80^@ + cos^2 85^@ is equal to