Trigonometric EquationHard
Question
If sin x + sin2 x = 1, then cos12x + 3cos10 x + 3cos8x + cos6x - 2 is equals to -
Options
A.0
B.1
C.-1
D.2
Solution
sin x = 1 - sin2x = cos2x
⇒ Now sin6x + 3sin5x + 3sin4x + sin3x - 2
= (sin2x)3 + 3(sin2x)2 sinx + 3(sin2x)2 + sin2x sinx -2
= (sin2x + sinx)3 -2 = 1 -2 = -1
⇒ Now sin6x + 3sin5x + 3sin4x + sin3x - 2
= (sin2x)3 + 3(sin2x)2 sinx + 3(sin2x)2 + sin2x sinx -2
= (sin2x + sinx)3 -2 = 1 -2 = -1
Create a free account to view solution
View Solution FreeMore Trigonometric Equation Questions
The general value of θ satisfying equation tan 3 θ - tan 2θ - tanθ = 0...Number of solutions of $\sqrt{3}cos2\theta + 8cos\theta + 3\sqrt{3} = 0,\theta \in \lbrack - 3\pi,2\pi\rbrack$ is:...The no. of solution of |cot x| = cot x + , x∈[0, 3π]...Which of the following is/are correct -...In triangle ABC, 2ac sin (A - B + C) =...