If there is a drop of blood in the left internal carotid artery it means that

There is an occlusion or blockage in the artery which can lead to a stroke

Explanation:

Blood vessels present in the neck that transports blood to the brain are known as internal carotid arteries. There are two internal carotid arteries, one on the left and the other on the right.

The widening of the carotid artery at the branch points is known as carotid sinus, which aid in the regulation of blood pressure

A drop of blood pressure in the left internal carotid artery it signifies blockage in the artery which can lead to a stroke.

find the sum of the two horizontal vectors and the sum of the two vertical vectors

isoceles right angled triangle