How Do I Correctly Calculate Vector C Using Unit Vectors?

[J89]

Homework Statement

Here's the entire question. But I ONLY NEED help with part B. Part A and Part C I know how to do:

Vector A is 3.60 m with an angle of 70 degrees and Vector B is 2.4 m with an angle of 30 degrees downward.

a) Write Vector A and Vector B in terms of the unit i and j (already completed)

b) Use unit vectors express vector C where vector C = 3.00A-4.00B

c) Find the magnitude and direction of Vector C

Homework Equations

Vector addition..

The Attempt at a Solution

Here's the solution for part A.

Vector A= 3.60sin70=3.38
3.60cos70=1.23
so Vector A in terms of i and j= 1.23i + 3.38j

Vector B= 2.4sin30=1.2
2.4cos30=2.1
so vector B in terms of i and j= -1.2i + -2.1j (negative since going down)

For part b, I did trial and error, however when I looked at the answer in the back of the book, it was completely wrong. The answer is 12.01i + 14.94j and the numbers I got is much lower. I cannot do part C without getting part B first. Help!

 

[Delphi51]

It says C = 3A - 4B
Replace A with your answer (1.23i + 3.38j) and B with your (-1.2i - 2.1j).
Expand and simplify. The final answer should be a number times i plus a number times j.

 

[jimvoit]

If angles are measured positive counter-clockwise from the positive x-axis (as standard) then your value for B is incorrect.