ddCalculate ri(t) · r2(t)] anddtri(t) x r2(t)] first by differentiatingdtthe product directly and then by applying the formulasdr2dri+dtdd ri(t) · r2(t)] = r¡(t) ·r2(t) anddtdr2d[ri(t) × r2(t)] = ri(t) xdri+dtx r2(t).dtdtr1(t) = 7ti + 9tj + 4t°k, r2(t) = t*kd.ar:(t) - r2(t)] =d[ri(t) x r2(t)] =dt

ddtr1(t).r2(t)=r2(t)dr1(t)dt+r1(t)dr2(t)dt ddtr1(t)×r2(t)=r1(t)×dr2(t)dt+dr1(t)dt×r2(t)

d Calculate ri(t) · r2(t)] and ri(t) × r2(t)] first by differentiating dt dt the product directly and then by applying the formulas dri d dr2 ri(t) · r2(t)] = ri(t) · r2(t) and dt dt dt dr2 dri x r2(t). d [r(t) x r2(t)] = r;(t) x dt dt dt r:(t) = 7ti + 9t²j +4t°k, r2(t) = t*k d [ri(t) · r2(t) : dt d r:(t) x ra(t) =