问题描述:
如图所示,在坡度一定的山坡 A 处测得山顶上一建筑物 CD 的顶端 C 对于山坡的斜度为15°,向山顶前进100米到达 B 处,又测得 C 对于山坡的斜度为45°,若 CD =50米,山坡对于地平面的坡角为 θ ,则cos θ =( ).
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最佳答案:
C |
在△ ABC 中,由正弦定理可知, BC = = =50( ),在△ BCD 中,sin∠ BDC = = = -1.由题图,知cos θ =sin∠ ADE =sin ∠ BDC = -1. |
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