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.
One particular type of lupus that generally affects only the skin is called discoid lupus. With this type of lupus, the skin problems consist of large red, circular rashes that may scar. Skin rashes are usually aggravated by sunlight. A common lupus rash called subacute cutaneous lupus erythematosus is often worse after exposure to the sun.