1 Angle of elevation and depression :
If an observer is at O and object is at then ÐXOP is called angle of elevation of P as seen from O.
If an observer is at P and object is at O, then ÐQPO is called angle of depression odf O as from P.
2 Some useful result :
(i) In any triangle ABC if AD : AB = m:n
ÐACD = a , ÐBCD = b & ÐBDC = q
then (m + n) cotq = m cota - ncotb
= ncotA – mcotB [ m-n Theorem]
(ii) d= h (cota - cotb)
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