Question
Question: The solution set of \((5 + 4\cos\theta)(2\cos\theta + 1) = 0\)in the interval \(\lbrack 0,2\pi\rbrac...
The solution set of (5+4cosθ)(2cosθ+1)=0in the interval [0,2π] is
A
{3π,32π}
B
{3π,π}
C
{32π,34π}
D
{32π,35π}
Answer
{32π,34π}
Explanation
Solution
(5+4cosθ)(2cosθ+1)=0
cosθ=4−5 which is not possible
∴2cosθ+1=0 or ∣sin2x∣=2π. ∣sin2x∣ π
Solution set is sinθ−3cosθ