If sin(θ) = 4/5 and θ is in Quadrant I, what is cos(θ)? A 3/5 B 4/3 C 5/4 D 1/5 ✓ Correct Answer: Option A sin²θ + cos²θ = 1. (4/5)² + cos²θ = 1. cos²θ = 9/25. cos θ = 3/5 (positive in QI). Practice ACT Exam Prep Quizzes → Browse All Questions Study Flashcards