Every chapter has it.
Function. Inequality. Trigonometric function. Sequence. Arrange and combine. Limit derivative calculus. Complex number. Vector. Space plane and straight line. Simple geometry. Analytical geometry. Mathematical thinking method of college entrance examination.
With point d as DE¡ÍAB in e,
And DC¡ÍCB, AB¡ÍCB,
¡à¡ÏDEB=¡ÏABC=¡ÏDCB=90£¬
¡à Quadrilateral DEBC is a rectangle,
In Rt¡÷ADE, ¡Ï ¦Á = 43, DE = CB =139m.