Calculating Vector Projection Using Trigonometry

[noname1]

Two vectors are given by avector = 3.5i + 4.5j and bvector = 2.0i + 5.0j. Find the following:

(a) avector x bvector

(b) avector ·bvector

(c) (avector + bvector ) · bvector

(d) the component of avector along the direction of bvector
these are the answers i got

a)8.5k
b) 29.5
c) 58.5
d)16.2

i know that a through c are correct but d is incorrect, i calculated d by

cos-1 (29.5/(5.7*5.39) = 16.2

the 5.7 came from sqrt(3.5²+4.5²)
5.39 came from sqrt(2²+5²)

thanks in advance

 

[ideasrule]

OK, so the angle between the vectors is 16 degrees. What did you do to calculate the projection of A on B?