In the figure, the area of quadrilateral ABCD is

In the figure, if congruent right triangles ABD and DCA share leg AD , then \alpha =

A right triangle has the length of one leg 11 cm and length of the hypotenuse 61 cm. Calculate the height of the triangle on the side of the hypotenuse.

In the figure, △ABC is right triangle. If AB=35 , a square with side 12 intersects with the triangle, what is the perimeter of the △ABC ?

In the figure on the right, △ABC is equilateral and △ADC is isosceles. If AC = 1 , what is the distance from B to D ?

The lengths of the 2 legs of right triangle △ABC shown below are given in inches 24, 32 respec. The midpoint of AB is how many inches from A ?

Given BD bisects ∠ABC , ∠A+∠C=180° . Prove AD=DC

Given quadrilateral ABCD , BC > BA , AD = DC , BD bisects ∠BAC . Prove ∠BAD + ∠C = 180°

In the triangle △ ABC , AB=AC , E is a point on AB , F is on extension line of AC , BE=CF , prove DE=DF 。

In △ABC , D is the midpoint of BC , EF crossing D intersects AB at point E and AE at F , and BE = CF , prove AE = AF

The obtuse Isosceles triangle ABC has two sides with length a and one side length b . The length of side a= 8 . The length of side b=3a . Find the perimeter of △ABC .

Given the right triangle paper sheet ABC , AC = 15cm, ∠B = 90°

(1) If AB=8.5cm , fold the triangle ABC to make point B fall on the side of AC as point E , the line made by folding is AD 。Find the length of EC .

(2) Assuming AB = x , first fold the triangle as (1) ,and then fold the triangle ADE along the line DE to make point A fall on the ray of EC as point F . In the folded shape, if the segment CF= \dfrac{1}{2}EF , what is the value of x ?