Derivatives of trigonometric functions
Differentiation · Mathematics
Study notes
Q: Differentiate: (a) x·cosx (b) tanx using quotient rule (verify sec²x). (a) cosx − x·sinx (product rule). (b) (sec²x·cosx... use sinx/cosx: [(cosx)(cosx)−(sinx)(−sinx)]/cos²x = 1/cos²x = sec²x ✓.