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As shown in the figure, the elevation angle of C is ∠ CAD = 30 ° from a, the elevation angle of C is ∠ CBD = 45 ° from B, and the angle of view is ∠ ACB when measuring a and B from C=______ Degree
Method 1: ∵ CBD is the outer angle of △ ABC, ∵ CBD = ∵ CAD + ∵ ACB, ∵ ACB = ∵ CBD - ∵ ACB = 45 ° - 30 ° = 15 °. Method 2: from the definition of adjacent complementary angle, ∵ CBA = 180 ° - CBD = 180 ° - 45 ° = 135 °. ∵ CAD = 30 °, ∵ CBA = 135 °, ∵ ACB = 180 ° - CAD - ∵ CBA =
As shown in the figure, the elevation angle of C is ∠ CAD = 30 ° from a, the elevation angle of C is ∠ CBD = 45 ° from B, and the angle of view is ∠ ACB when measuring a and B from C=______ Degree
Method 1: ∵ - CBD is the outer angle of △ ABC, ∵ - CBD = ∵ CAD + ∵ ACB, ∵ - ACB = ∵ CBD - ∵ ACB = 45 ° - 30 ° = 15 °. Method 2: from the definition of adjacent complementary angle, ∵ - CBD = 180 ° - 45 ° = 135 °. ∵ - CAD = 30 °, ∵ CBA = 135 °, ∵ - ACB = 180 ° - CAD - ∵ CBA = 180 ° - 30 ° - 135 ° = 180 ° - 165 ° = 15 °
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