Posted by **maker** on Sunday, May 26, 2013 at 10:54am.

in the diagram below.A,B and C are three points in the same horizontal plane and AD is a vertical tower.AC=AB=x and DC=DB.the angle of elevetion of D from C is alpha and DB^C=theta

1.express DC in terms of x trigonometry value of alpha

2.prove that BC=2xcostheta/cos alpha