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.
Signs of lupus include: 1  Fatigue or malaise. 2  Joint pain, stiffness or swelling. 3  Muscle pain or weakness. 4  Fever with no known cause. 5  A red, butterfly-shaped rash across the nose and cheeks. 6  Other rashes, particularly on areas of the body exposed to the sun. 7  Pain in the chest when taking a breath.