Difficulty: Easy
Correct Answer: 9 √3 cm2
Explanation:
Introduction / Context:
Knowing the diagonal and its angle with a side determines both side lengths via basic trigonometry, from which the area follows directly.
Given Data / Assumptions:
Concept / Approach:
tan 30° = b/a = 1/√3 ⇒ b = a/√3. Also, d² = a² + b². Substitute b and solve for a, then compute area A = a·b.
Step-by-Step Solution:
Verification / Alternative check:
Compute diagonal from a and b: √(27 + 9) = √36 = 6 (consistent).
Why Other Options Are Wrong:
9 cm² corresponds to b = 3 with a = 3, which would make tan 30° = 1; 27 and 36 cm² are incompatible with d = 6.
Common Pitfalls:
Using sin or cos instead of tan to relate a and b at the specified angle.
Final Answer:
9 √3 cm2
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