This problem involves the dot product.
You must provide all info for position vector m. Your (2,) is inadequate.
Supposing that the terminal point of vector m were (2,3), then
m dot n would equal 8, or 8 = 2*2+3*y. Then 8 = 4 + 3y, and 4 = 3y, and y =3/4.
Please type in the terminal point of vector m and then answer this question following the above example.
