Prosimo, rešite q 80?

Odgovor:

možnost (4) je sprejemljiva.

Pojasnilo:

Glede na to, # AB = AC = BD # in #AC_ | _BD #.

# rarrAB = AC #

# rarr / _B = / _ C #

# rarr90-a + 90-d = d #

# rarra = 180-2d #…..1

Tudi, # rarrAB = BD #

# rarr / _A = / _ D #

# rarra + b = 90-b #

# rarra = 90-2b #….2

Iz 1 in 2 imamo, # rarr180-2d = 90-2b #

# rarrd-b = 45 #….3

Zdaj, # / _ C + / _ D #

# = / _ BCA + / _ BDA = 90-b + d = 90 + 45 = 135 #

Odgovor:

# angleC + angleD = 135 ^ @ #

Pojasnilo:

Let # angleABD = x #,

dan # AB = BD, => angleBDA = (180-x) / 2 #

let # angleKBD = y #, dan # AB = AC, => angleACB = kotAAB = x + y #, V #DeltaCBE, => barva (rdeča) (x + 2y = 90 ^ @) #

# angleC + angleD = angleAB + kotBDA = x + y + (180-x) / 2 #

# = x + y + 90-x / 2 #

# = x / 2 + y + 90 #

# = (x + 2y) / 2 + 90 #

#=90/2+90=45+90=135^@#