Trigonometry & Inverse Trigonometry
Trigonometric Equations
Grade 11
Question:
<p>If 0 < <i>x</i> < 2π, then the number of real values of <i>x</i> which satisfy the equation <i>cos x</i> + <i>cos 2x</i> + <i>cos 3x</i> + <i>cos 4x</i> = 0 is:</p>
<p>(a) 3</p>
<p>(b) 5</p>
<p>(c) 7</p>
<p>(d) 9</p>
Step-by-Step Solution
Key Concept: Use sum-to-product formulas to group and simplify the cosine terms.
<p>Solution not provided in extracted text.</p>
Correct Answer: C