Question

The Vector v has a length of 15 and points at an angle of 30 degrees. The Vector u has a length of 17 and points at an angle of 55 degrees. What is u*v?

I know to get my answer I need to use this format |u|*|v|*cos(theta)
however I am stuck at setting up my vectors I only know <15,?> and <17,?>. Your help is appreciated greatly!

Answer 1

have you learned that any linear vector can be expressed as
(rcosØ , rsinØ) where r is the magnitude and Ø is the angle it makes with the horizontal.

so vector u = (15cos30°, 15sin30°)
= (15√3/2 , 15/2)
and
vector v = (17cos55, 17sin55)

u*v = 126.666600047 + 104.441885647)
or appr 231.1

check:
the angle between them would be 25°
231.1 = 15*17cosØ
cosØ = 0.906307787
and cos 25 = 906307..
my answer for u*v is correct

Answer 2

Thank you very much Reiny I was stumped on that but thanks to your assistance I was able to solve the problem. Thank you very much!