1. Sine, cosine and tangent formulas of sum and difference of two angles

Emphasis: Through exploration and discussion, eleven formulas of the difference between two angles and trigonometric function are derived, and their internal relations are understood.

Difficulties: exploration and proof of cosine formula of two-angle difference.

2. Simple trigonometric identity transformation

Key points: master the contents, ideas and methods of trigonometric transformation and understand its characteristics.

Difficulties: Flexible application of the formula.

Several explanations of trigonometric function;

1. We only need to know the arc length formula, which can be simply applied, and it doesn't need to be deepened when applied.

2. Prove trigonometric identity and evaluation calculation with the basic relationship of trigonometric function with the same angle, and be skilled in supporting roles and calculation of sin and cos.

3. The problem of finding the angle of trigonometric function is known, and it can meet the requirements of teaching materials without expansion.

4. Grasp the function y=Asin(wx+j) image, monotone interval, symmetry axis, symmetry point, special point and maximum value.

5. Sum-and-difference multiplication, sum-and-difference multiplication and half-angle formula are just exercises and do not need to be memorized.

6. Sine, cosine and tangent formulas of sum and difference of two angles