question_answer

If a round balloon of radius 'a' metres subtends an angle \[\theta \] at the eye of an observer while the angle of elevation of its centre is\[\phi \], then the height of the centre of the balloon is

A)  \[a\,\,\sin \,\,\frac{\phi }{2}\,\,\,\operatorname{cosec}\theta \]       

B)  \[\frac{a}{2}\,\,\sin \phi \,\,\operatorname{cosec}\,\,\frac{\theta }{2}\]

C)  \[\frac{a}{2}\,\,\sin \,\,\frac{\phi }{2}\,\,\operatorname{cosec}\theta \]      

D)  \[a\,\,\sin \,\,\phi \,\operatorname{cosec}\,\,\frac{\theta }{2}\]

E)  None of these