21.
(2020高三上·广东月考)
微型无人机航空摄影测量系统具有运行成本低、执行任务灵活等优点,正逐渐成为航空摄影测量系统的有益补充.为了测量一高层地标建筑AB的高度,无人机在空中适当高度的水平平面DEC内测得相关数据如下:在D位置测得顶端A的仰角和底端B的俯角分别为
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E60%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmo%3E%E2%88%98%3C%2Fmo%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
、
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E45%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmo%3E%E2%88%98%3C%2Fmo%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
,建筑上的点C的方位角为
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E98%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmo%3E%E2%88%98%3C%2Fmo%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
;在E位置测得A的仰角和B的俯角分别为
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E45%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmo%3E%E2%88%98%3C%2Fmo%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
、
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E30%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmo%3E%E2%88%98%3C%2Fmo%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
,建筑上的点C的方位角为
![](//math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmrow%3E%3Cmsup%3E%3Cmrow%3E%3Cmn%3E68%3C%2Fmn%3E%3C%2Fmrow%3E%3Cmo%3E%E2%88%98%3C%2Fmo%3E%3C%2Fmsup%3E%3C%2Fmrow%3E%3C%2Fmath%3E)
.D、E间相距220米.求建筑AB的高度.
(说明:本题中将建筑AB看作与地面所在水平平面垂直于底端B的线段.方位角是水平面内从某点的指北方向线起按顺时针方向到目标方向线之间的角.)