show that : `sin^2 alpha + sin^2(alpha +( 2pi)/n) +sin^2(alpha +( 4pi)/n) + .....` ` n ` terms ` = n/2`

Show that 4 sin alpha.sin (alpha + pi/3) sin (alpha + 2pi/3) = sin 3alpha

Prove that: sin^2theta=sin^2alpha , then theta=npi+-alpha,n in Z

Show that: sin^2 alpha + sin^2 beta + 2sinalpha sinbeta cos(alpha+beta)=sin^2 (alpha+beta)

Evaluate sin(pi/n)+sin((3pi)/n)+sin((5pi)/n)+........ to n terms.

The value of sin pi/n + sin (3pi)/n+ sin (5pi)/n+... to n terms is equal to

If sinalpha, sin^2alpha, 1 , sin^4alpha and sin^6alpha are in A.P., where -pi < alpha < pi, then alpha lies in the interval

Prove that 2 sin^2 beta + 4 cos(alpha + beta) sin alpha sin beta + cos 2(alpha + beta) = cos 2alpha

Find sum of sin2alpha+sin3alpha+.......+sinnalpha where (n+2)alpha = 2 pi

If a cos^3 alpha +3acosalpha*sin alpha = m and a sin^3alpha +3a cos^3alpha sin^3alpha = n then (m + n)^(2/3) + (m-n)^(2/3)

If cos^(-1)x-cos^(-1)y/2=alpha,t h e n4x^2-4x ycosalpha+y^2 is equal to 4 (b) 2sin^2alpha (c) -4sin^2alpha (d) 4sin^2alpha