Why are swept wings used on high-speed aircraft and what are their aerodynamic effects?

Swept wings delay the onset of transonic drag rise by reducing the effective Mach number normal to the leading edge (Mn = M*cos(sweep)). This allows higher cruise speeds before wave drag becomes significant. However, swept wings have disadvantages: reduced lift curve slope, tip stall tendency (spanwise flow), lower maximum lift, increased structural weight, and reduced low-speed performance. The typical sweep angle is 25-35 degrees for subsonic transports and up to 60+ degrees for supersonic aircraft. Design must address tip stall through washout, leading edge devices, or fences.