Consider the function f(x, y) = -3x^2-2y^-2. Find the directional derivative of f at the point (1,-4) in the direction given by the angle theta = 2pi/5. Find the unit vector which describes the direction in which f is increasing most rapidly at (1,-4). I have already confirmed the directional derivative to be exactly -6cos(2pi/5) + 16sin(2pi/5) I believed the unit vector should have been (cos(2pi/5), sin(2pi/5)), but when I checked my answer the only correct part was the sin(2pi/5). If the other part is not cos(2pi/5), then what is it and How would that be calculated or inferred?

a

step-by-step explanation:

the answer is a

if gloria has "carry over" minutes, (that is, any minutes paid for but not used in a month can be applied to her payment for minutes in the next month,) her total usage for the three months is: total minutes = 320 + 243 + 489 = 1052 minutes number of 200 minute blocks = 1052/200 = 5 r52 (that is 5 with a remainder of 52) rounding up the number of 200 minute blocks gives her usage for the three months as 6 blocks. the cost for six blocks is 6 x $25 = $150 she also has 200 - 52 or 148 carry over minutes if gloria pays each month and unused minutes are lost, applying the rounding up procedure to each month gives: first month usage of 320 minutes rounds up to 2 blocks of 200 minutes for a payment of 2 x $25 = $50 second month usage of 243 minutes rounds up to 2 blocks of 200 minutes for a payment of 2 x $25 = $50 third month usage of 489 minutes rounds up to 3 blocks of 200 minutes for a payment of 3 x $25 = $75 total payments for the three months are $50 + $50 + $75 = $175 get the plan with carry over minutes!