The partial derivative of 4q1q2 with respect to q1 is solved by thinking of q2 as a constant, C. So the derivative of 4q1C is just 4C, or 4q2 (The derivative of 4q1 is 4 and that 4 is multiplied by C, so 4C or 4q2). The partial derivative of 4q1q2 with respect to q2 is solved by thinking of q1 as a constant, C. So the derivative of 4Cq2 is just 4C, or 4q1.
Sir why partial derivative is not done here with 4q¹q²?
The partial derivative of 4q1q2 with respect to q1 is solved by thinking of q2 as a constant, C. So the derivative of 4q1C is just 4C, or 4q2 (The derivative of 4q1 is 4 and that 4 is multiplied by C, so 4C or 4q2). The partial derivative of 4q1q2 with respect to q2 is solved by thinking of q1 as a constant, C. So the derivative of 4Cq2 is just 4C, or 4q1.