Prove that `2sin2^0+4sin4^0+6"sin"6^0+.......+180sin180^0=90cot1^0dot`

Prove that 2 sin 2^(@)+4sin 4^(@)+6sin 6^(@)+........+180sin 180^(@)=90 cot 10^(@) .

The average value of sin2^@,sin4^@, sin6^@.........sin180^@ is (i) 1/90 cos1^0 (ii) 1/90 sin1^0 (iii) 1/90cot1^0 (iv) none of these

Prove that: cos18^0-sin 18^0=sqrt(2)sin27^0

Prove that: sin10^0sin30^0sin50^0sin70^0=1/(16)dot

Prove that sin(-420^0)(c0s390^0)+cos(-660^0)(sin330^0)=-1

The roots of the equation 4x^2-2sqrt(5)x+1=0,a r e (a) sin36^0,sin18^0 (b) sin18^0,cos36^0 (c) sin36^0,cos18^0 (d) cos18^0,cos36^0

The value of expression (2(sin1^0+sin2^0+sin3^0+...+sin89^0))/(2(cos1^0+cos2^0++cos44^0)+1) (a) sqrt(2) (b) 1/(sqrt(2)) (c) 1/2 (d) 0

Prove that sinA+sin(120^(@)+A)+sin(240^(@)+A)=0 .

Prove that sin 50^(@)-sin 70^(@)+cos 80^(@)=0 .

Solve: sin2x +sin6x -sin4x=0 .