Chapter 2 - The Derivative - 2.5 Derivatives of Trigonometric Functions - Exercises Set 2.5 - Page 151: 2

$=-\frac{10}{x^{3}}+cosx$

Convert the polynomial into a power of $x$, giving you $5x^{-2}$, Finally, split the derivative into two separate, single derivatives. The polynomial derivative uses power rule ($[x^{n}]'=nx^{n-1}$) while the derivative of $sinx$ is $cosx$. Therefore, the derivative is $-5(2){x^{-2-1}}+cosx=-\frac{10}{x^{3}}+cosx.$