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Example 3 If cot a
= 3 and p < a
< 3p /2 . Find 4 sin a
+ 2 cos a
Solution :
p < a
< 3p /2 means a lies in IIIrd Quadrant.
\ sin a
and cos a are negatives.
Example 4
if tan 
Solution : since p
< A < 3/2 p, A lies in the IIIrd
Quardrant.
\ Both csc A and
sec A are negative.
Example 5
5 tan  Find the
value of cosec A - sin B.
Solution :
Example 6 
where A and B are angles in the second Quadrant.
Prove that 4 cos A+ 3 cos B = -5.
Solution : 1) We have 
is II Quadrant.
From cos2A = 1- sin2A we
get
Example 7 If sin 
, determine the values of tan 
, sec , and csc
.
Solution : We know that m2+
n2)2- (m2- n2)2
= 4 m 2 n2
Given that 
observing the adjoining fig it follows that
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