Answer:
7/25
Step-by-step explanation:
θ lies in quadrant ii
so 2θ lies in quadrant iv
csc θ=5/3
sin θ=3/5 (sin θ=1/csc θ)
[cos(α+β)=cosαcosβ-sinαsinβ]
cos (2θ)=cos(θ+θ)=cos θ cos θ-sin θ sin θ=cos² θ-sin ²θ=1-sin²θ-sin²θ=1-2sin²θ
=1-2 (3/5)²
=1-2(9/25)
=1-18/25
=(25-18)/25
=7/25
