Question 4 • Precalculus
The largest angle is opposite the longest side, 20 units, and the smallest angle is opposite the shortest side, 15 units. By the law of cosines, these angles are approximately cos⁻¹((15² + 18² − 20²)/(2·15·18)) = 74° and cos⁻¹((20² + 18² − 15²)/(2·20·18)) = 46°. Their difference is about 28°, so the answer is 28 degrees.
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