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Nusret Balcı TMUA Paper 1 · Q6

Paper 1TrigonometryAlgebra

Let k∈Rk\in\mathbb R. Consider the equation

(1+3cos⁡θ)2=kcos⁡2θ,0∘≤θ≤360∘.(1+3\cos\theta)^2=k\cos2\theta,\qquad0^\circ\le\theta\le360^\circ.

For which values of kk does the equation have exactly four distinct solutions in the given interval?

Ak<−9k<-9
B−9<k<−1-9<k<-1
C−1<k<0-1<k<0
D0<k<10<k<1
E1<k<91<k<9
Fk<0 or k>72k<0\text{ or }k>\frac72
Gk<0 or k>4k<0\text{ or }k>4
Hk<0 or k≥16k<0\text{ or }k\ge16

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