Concept:Anti-derivative is the same as integration.Some useful formulas are:\(\rm \frac{d}{dx} (sinax) = a.cos(ax)\)Calculation:The anti-derivative of cos7x is a function of x whose derivative is cos7x.So. we can write,\(\rm \frac{d}{dx} (sin7x) = 7cos7x\)So, cos7x = \(\rm \frac{1}{7} \frac{d}{dx} (sin7x)\)Further, cos7x = \(\rm \frac{d}{dx} ( \frac{1}{7}sin7x)\)So, the anti-derivative of cos7x is \(\rm \frac{1}{7}sin7x\)