differentiation

Differentiate y=csc(2-x²) w.r.t. x.
答案係 -2x csc(2-x²) cot(2-x²)
但係我計到
y'=[d/d(2-x²) ·csc(2-x²)][d(2-x²)/dx]
d csc(2-x²)呢舊唔係 -csc(2-x²) cot(2-x²) 咩?
之後d(2-x²)唔係-2x咩?
點解個答案唔係 2x csc(2-x²) cot(2-x²)?
我本書好少會錯..我錯左咩?

Let y = 2x + 1/x². Find dy/dx from first principles.
我想問呢題係咪真係要爆晒所有野出黎? 會唔會有d快d既方法? thx

唔好意思問多題= ="
Differentiate y = 2 sec x w.r.t. x from first principles.
完全唔知點約走個Δx....

唔該晒~