常见的求导公式

• (tanx)' = sec^2 x = 1/cos^2 x
• (cotx)' = -csc^2 x = 1/sin^2 x
• (secx)' = tanx * secx
• (-cscx)' = cotx * cscx
• (arcsinx)' = 1/√1-x^2
• (arccotx)' = -1/√1-x^2
• (arctanx)' = 1/1+x^2
• (arccotx)' = -1/1+x^2

降幂公式

sin^2 x = 1-cos2x/2

cos^2 x = 1+cos2x/2