Product Rule. If the two functions f(x) and g(x) are differentiable (i.e. the derivative exist) then the product is differentiable and, The proof of the Product Rule is shown in the Proof of Various Derivative Formulas section of the Extras chapter.
Inflammation is the most common reason for muscle pain and aches. Any time that major inflammation exists (strep throat, hepatitis, cancer, lupus, acute heart attack, etc.), signs and symptoms often include fevers, sweats, chills, fatigue, weight loss, and various muscle aches, pains and weakness.
Fatigue: Lupus causes mild to extreme fatigue. Even mild cases of lupus make it hard to do daily activities and exercise. Increased fatigue is a classic sign that a symptom flare is about to occur. Joint and muscle pain: Joints may be painful, red, and warm. They may swell. Morning stiffness may also be felt.