Hello, this is a question from a pure mathematics textbook: (2D vectors) The vectors a and b are of equal magnitute k (k does not equal 0), and the angle between a and b is 60 degrees. If c=3a-b and d=2a-10b A) Show that c and d are perpendicular vectors. (Sadler, A.J., Thorning, D.W.S (2007, pg.63). Understanding Pure Mathematics, Glasgow: Oxford Universty Press). c.d=0 =|c||d|cos(90) Therefore, c.d/|c||d|=cos(90) 'Normally' for the dot product, the coefficients of the 'i' component of the two vectors are multiplied togeather, and the same process is applied to the j components, then they are added togeather. I would attempt the question, but to be honest I'm not sure what steps to take; since my base vectors a and b are not orthogonal. Am I using the correct method? An answer would be much appreciated, I apologise for the language used and the presentation, I hope its accurate.