Introduction to Trigonometry
CH08 Question Bank
CBSE_CH08_QUESTION_BANK
Grade 10
Question:
If $\text{cosec}\,\theta=\dfrac{13}{12}$, find $\sin\theta$ and hence find $\cos\theta$.
Step-by-Step Solution
Key Concept: Use the reciprocal relationship to find $\sin\theta$, then apply $\sin^2\theta+\cos^2\theta=1$.
$\sin\theta=\dfrac{1}{\text{cosec}\,\theta}=\dfrac{12}{13}$. [1.0 Mark]
$\cos^2\theta=1-\dfrac{144}{169}=\dfrac{25}{169}\Rightarrow\cos\theta=\dfrac{5}{13}$. [1.0 Mark]
Correct Answer:
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