Introduction to Trigonometry
CH08 Question Bank
CBSE_CH08_QUESTION_BANK
Grade 10
Question:
If $\cos A=\dfrac{1}{2}$, find the value of $3\cos A - 4\cos^3A$.
Step-by-Step Solution
Key Concept: Substitute the given value and evaluate directly.
$3\cos A-4\cos^3A=3\left(\dfrac12\right)-4\left(\dfrac12\right)^3=\dfrac32-\dfrac{4}{8}$. [1.0 Mark]
$=\dfrac32-\dfrac12=1$. [1.0 Mark]
Correct Answer:
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