1. The problem statement, all variables and given/known data The projectile A is being tracked by the radar at O. At a given instant, the radar readings are θ = 30degrees, R = 2000m, dR/dt = 200 m/s, and d^2R/dt^2 = 20 m/s^2. Determine the speed of the projectile at that instant. THE ANSWER AT THE BACK IS 299.7m/s [PLEASE SEE ATTACHMENT FOR PROBLEM & FIGURE] 2. Relevant equations I've used the Vr = dR/dt & Vθ= R(dθ/dt) 3. The attempt at a solution I've worked out an equation which is cos30=x/2000 --> x = 1732.05 dR/dt = 1732.05 (dθ/dt)(secθtanθ) 200 = 1732.05 (dθ/dt)(sec30tan30) dθ/dt = 0.1732 deg/sec? And using V^2 = Vr + Vθ I didn't get 299.7m/s So I'am wrong.