1. ## vector addition calc 3

I'm trying to do this homework problem but I keep getting an answer that is not given. Can someone tell me what I am doing wrong please. This is for University level calc 3.

so I start by naming the vectors.V is the direction the plane is now heading. V1 is the original direction of the plane. V2 is the direction of the wind.

V = V1 + V2

V1 = 600(cos148i+sin148j)
V2 = 80(cos45i+sin45j)

next I distributed, combined like terms and factored out i and j
V = (600cos148+80cos45)i + (600sin148+80cos45)j

I plugged that into my calculator and got
V = <-452.7i + 374.5j>

To find the speed I found the length of vector V
||V|| = sqrt[ (-452.7)2+374.52] = 587.5 km/hr

That isn't one of the options.. am i wrong"?

2. ## Re: vector addition calc 3

Originally Posted by shmiks
I'm trying to do this homework problem but I keep getting an answer that is not given. Can someone tell me what I am doing wrong please. This is for University level calc 3.

so I start by naming the vectors.V is the direction the plane is now heading. V1 is the original direction of the plane. V2 is the direction of the wind.

V = V1 + V2

V1 = 600(cos148i+sin148j)
V2 = 80(cos45i+sin45j)

next I distributed, combined like terms and factored out i and j
V = (600cos148+80cos45)i + (600sin148+80cos45)j

I plugged that into my calculator and got
V = <-452.7i + 374.5j>

To find the speed I found the length of vector V
||V|| = sqrt[ (-452.7)2+374.52] = 587.5 km/hr

That isn't one of the options.. am i wrong"?
Your method is correct, but some numbers are off. I would guess that you are rounding the numbers. I usually keep all the digits when I do a calculation. I'm getting Vx = -452.260315 km/h, Vy = 397.64713 km/h, and |V| = 602.214776 km/h.

-Dan

3. ## Re: vector addition calc 3

ahh you are right, I used an online calc instead of my TI-89 and got 587.2 I must have my max characters set too low or something. Thank oyu for the help