In the image above, there is a formula for the delay of a signal at a given sensor 'i' in an antenna array. I don't understand how they arrived at that formula.
Each antenna array element is separated by a distance of 'd' and we know the signal hits the array at an angle 'theta'. Dividing by 'c' gives us the time taken for light to travel the additional distance, but I don't see how the quantity 'dsin(theta)' represents the extra distance. Would appreciate any clarification.