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.
Lupus symptoms vary widely, and they come and go. The times when symptoms get worse are called relapses, or flares. The times when symptoms are under control are called remissions. Common symptoms include feeling very tired and having joint pain or swelling (arthritis), a fever, and a skin rash .