# Angles of quadrilaterals - Wiki

• In the figure below, ABCD is a rhombus. `/_`ABC `= 102^o` and `/_`CAE `= 19^o`. Find `/_`EAB. Ans: _BLANK_`^o`

Triangle BAC is an isosceles triangle.

< BAC = (180o - 102o`-:` 2 = 78o `-:` 2 = 39o

< EAB = 39o - 19o = 20o

• In the figure below, a rectangular piece of paper is folded along AD as shown. Given that EFBC is a straight line, find (a) `/_`EDF. (b) `/_`DFC. Ans: (a) _BLANK_ [2] Ans: (b) _BLANK_ [1]

(part a):

`/_` BDA= 180o - 90o - 70o = 20o

`/_` EDF = 90o - 20o - 20o = 50

(part b)

`/_` DFE = 180o - 90o - 50o = 40o

`/_` DFC = 180o - 40o = 140o

• In the diagram below, ACF is a right-angled triangle, DEGH is a square and ABDH is a rhombus. Given that AB `=` BH, find `/_`AFC. Ans: _BLANK_`^o` [4]