i41 tinypic com/2qna74k png

(add the periods)

For the vectors in the figure, with a = 6.4, b = 2.5 and c = 6.87. Calculate a(dot)b
calculate a(dot)c
calculate b(dot)c

I got 0 for a(dot)b but the same method (ac*cos(theta)) does not work for the other two, please help.

If it does not work, you are not using a common angle reference. Set a line from which you measure all the angles from CLOCKWISE.

I cannot see your picture.

Thank you for responding. You have to replace the spaces with periods (.)

To calculate the dot product between two vectors, you need to multiply the corresponding components of each vector and then sum up the results. In this case, you have three vectors a, b, and c, with given magnitudes a = 6.4, b = 2.5, and c = 6.87.

For a dot b, the dot product is calculated as follows:

a · b = a1 * b1 + a2 * b2

Substituting the magnitudes:

a · b = 6.4 * 2.5

a · b = 16

Therefore, the dot product of a and b is 16.

Now, let's calculate a · c. The dot product of a and c is calculated in the same way:

a · c = a1 * c1 + a2 * c2

As you mentioned, using the formula ac * cos(θ) does not seem to be working for you. However, it is important to note that the formula ac * cos(θ) is used when you have the angle between the vectors and their magnitudes. If the angle is not provided, you cannot directly use this formula.

To proceed with the calculation, we need the components of vector c. Unfortunately, I am unable to view the figure or the image you described. Please provide the components of vector c, and I will assist you further in calculating a · c and b · c.