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.
Discoid lupus erythematosus, which mainly affects the skin. The symptoms of this form of lupus include a rash on the face, scalp, or elsewhere. The rash may last for days or years, and can recur. Drug-induced lupus, which is triggered by certain medications, usually goes away when the medicine is stopped. The symptoms in this form of lupus may be milder.