The photo reminds me of the happy time I spent in Shanghai.

Directions According to the given information,you are required to write A Letter to a Friend in about 1OO words. The letter is required to be written on the Answer Sheet.

钢筋的力学性能指标包括___________、___________、___________、___________，其中___________和___________是检验钢筋塑性性能的两个指标。

求微分方程dy/dx +y=e-x的通解．

后张法构件的第一批损失σⅠ由________构成，第二批损失σⅡ由________构成。

设x∈，则arcsinx+arccosx=_________．