Home › TS EAPCET (Engineering) › Mathematics › Trigonometric Functions › Counting the roots of cos x + cos 3x = 0 on [0, …
Counting the roots of cos x + cos 3x = 0 on [0, π], one gets
A1
B2
C4
D3
Answer & Solution
Correct answer: D. 3
The sum equals 2 cos 2x cos x, which vanishes at x = π/4, π/2 and 3π/4.
Related questions
Inside (0, π/2), the angle where tan x equals its own reciprocal isThe least positive root of the equation sin 2x = sin x isAdding every root of 2 sin x cos x = sin x on [0, π] givesBetween 0 and 2π inclusive, how many angles satisfy sin 2x = 1?Solving sin x = sin α completely, with n an integer, givesTangent takes positive values in which pair of quadrants?A point has sine 3/5 and sits in the second quadrant; its cosine isHalving the angle inside a cosine stretches its repetition length to