2019教师资格证数学科目三
f x1=a2+b2sin(x1+φ)，f x2=a2+b2sin(x2+φ) f x1≠f x2，所以x1≠x2
f′x1=a2+b2cos(x1+φ)，f′x2=a2+b2cos(x2+φ)所以f′x1≠f′x2
