inequalities of trigo
p124 q12 re.ex5
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We have to "talk" our way through these . .
Find the values of in the range
We have: .
Clearly, we are dealing with multiples of 45°: .
When is between ?
Examine the unit circle . . .
Answer: .
This one takes a bit more "talking" . . .
We have: .
The product of two factors is negative if the factors have opposite parity.
Hence, there are two cases to examine . . .
. . is negative in quadrants 2 and 3: .
. .
The intersection of the two sets is: .
. . is positive in quadrants 1 and 4: .
. .
The intersection of the two sets is: .
The solution is: . . . . Quadrants 2 and 3