Given that x x\,x is measured in radians, prove, from first principles, that the derivative of sinx \sin x\,sinx is cosx\cos xcosx.
You may assume the formula for sin(A±B)\sin(A \pm B)sin(A±B), and that as h→0h \to 0h→0, sinhh→1\dfrac{\sin h}{h} \to 1hsinh→1 and cosh−1h→0\dfrac{\cos h - 1}{h} \to 0hcosh−1→0.
333 exam-style questions on WJEC A Level Maths 3.6 Differentiation (A-level only), covering 3.6.1 Differentiation (A-level only), 3.6.2 Differentiation (A-level only), 3.6.3 Differentiation (A-level only), 3.6.4 Differentiation (A-level only), 3.6.5 Differentiation (A-level only), 3.6.6 Differentiation (A-level only), 3.6.7 Differentiation (A-level only), and 3.6 Differentiation (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.