" 8.(i) Show that "cos A=(cos3A)/((2cos2A-1))," Hence find the value of cos "169

Show that CosA=(Cos3A)/(2Cos2A-1) . Hence find the value of Cos15^(@)

Show that sin A= (sin 3A) /(1+2 cos 2A) . Hence find the value of sin 15^(@).

Show tha: cos4A=1-8cos^2A+8cos^4A .

For A= in (0,pi/4),"if"(1+(cos3A)/(cosA))+(1+(cos6A)/(cos2A))+(1+(cos9A)/(cos3A))+(1+(cos12 A)/(cos4A))=0, then find the value of (csc A - scc 2A).

If 1+cos^2A=3 cos AsinA , find the value of cotA.

(i) if sin x= (1)/(3) find the value of sin 3x (ii) if cos x= (1)/(2) , find the value of cos 3x

Find the value of cos^-1(cos((3pi)/2))

If 7A = pi, show that cos A cos 2 A cos 3 A = 1/8 .

Show that cos(pi/7)cos((2pi)/7)cos((3pi)/7)=1/8