Without using the law of sines, explain why no triangle ABC can exist that satisfies A = 103° 20', a = 14.6 ft, b = 20.4 ft.

검증된 단계별 안내

Recall that in any triangle, the sum of the interior angles must be exactly 180°.

Given angle \(A = 103° 20'\) (which is an obtuse angle), note that the other two angles, \(B\) and \(C\), must sum to \(180° - 103° 20' = 76° 40'\).

Since side \(a\) is opposite angle \(A\), and side \(b\) is opposite angle \(B\), consider the relationship between sides and angles: the larger side is opposite the larger angle.

Here, side \(b = 20.4\) ft is longer than side \(a = 14.6\) ft, so angle \(B\) should be larger than angle \(A\) if the triangle exists, but angle \(A\) is already greater than 90°, making it the largest angle.

This contradiction shows that no triangle can exist with \(A = 103° 20'\), \(a = 14.6\) ft, and \(b = 20.4\) ft, because the side lengths and angle measures are inconsistent with the triangle inequality and angle-side relationships.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Triangle Angle Sum Property

The sum of the interior angles in any triangle is always 180°. Knowing one angle and the relationship between sides helps determine if a triangle can exist. If given angles and sides contradict this property, the triangle is impossible.

Relationship Between Sides and Opposite Angles

In a triangle, larger sides are opposite larger angles, and smaller sides opposite smaller angles. If a given side length is smaller than another but opposite a larger angle, this contradicts the fundamental side-angle relationship, indicating no such triangle can exist.

Triangle Inequality Theorem

The sum of the lengths of any two sides of a triangle must be greater than the third side. This theorem ensures the sides can physically connect to form a triangle. Violations of this rule mean the triangle cannot be constructed.