Trim and Extend

Shorten or lengthen objects to meet the edges of other objects

Trim

Modify panel > Trim

Cross-select the cutting edges
Press Enter

Cross-select the portion you want to trim

Repeat Trim command
Select the arc as the cutting edge

Cross-select the portion you want to trim

Extend

Modify panel > Extend

Select the arc as a boundary edge

Cross-select the 2 lines to extend

Trim and Extend

Repeat Extend command

Cross-select all objects act as boundary and cutting edges

Press Enter

Cross-select 2 lines and extend to the arc

Hold the Shift key, cross-select the 2 lines to trimed

Hold the Shift key, cross-select the 2 circles to trimed