Answer:
Step-by-step explanation:
sin θ= - cos θ
if : cos θ ≠ 0
you have : tan θ = -1
tan θ = - tan π/4
tan θ = tan(- π/4 )
θ = - π/4 +kπ k ∈ Z
calculate: k when θ is in quadrant IV : 3π /2 ≤ θ ≤2π
3π /2 ≤ - π/4 +kπ ≤2π
add π/4: 3π /2 + π/4 ≤ - π/4 +kπ+π/4 ≤2π +π/4
7π/4 ≤ kπ ≤9π/4
7/4 ≤ k ≤9/4
1.75 ≤ k ≤ 2.25
k ∈ Z : k =2
so : θ = - π/4 +2π
θ = 7π/4
θ = 7(180°)/4 = 315°
