7cosθ and tanθ from sinθ

sin θ = 3/5 and θ is in the second quadrant. Find cos θ and tan θ.

Since sinθ = 3/5 and θ is in quadrant 2, cosθ = −4/5 and tanθ = −3/4. Using sin²θ+cos²θ=1 gives cos²θ=16/25, and cosine is negative in Q2; tan is sine over cosine.