Trapezoid v3

The isosceles trapezoid has an angle at a first base 40 degrees less than the angle at the second base. How large angles has this trapezoid?

Correct answer:

a =  70 °
b =  110 °
c =  110 °
d =  70 °

Step-by-step explanation:


a=d
b=c
a+b+c+d = 360
a+40 = b

a-d = 0
b-c = 0
a+b+c+d = 360
a-b = -40

Row 3 - Row 1 → Row 3
a-d = 0
b-c = 0
b+c+2d = 360
a-b = -40

Row 4 - Row 1 → Row 4
a-d = 0
b-c = 0
b+c+2d = 360
-b+d = -40

Row 3 - Row 2 → Row 3
a-d = 0
b-c = 0
2c+2d = 360
-b+d = -40

Row 4 + Row 2 → Row 4
a-d = 0
b-c = 0
2c+2d = 360
-c+d = -40

Row 4 - -1/2 · Row 3 → Row 4
a-d = 0
b-c = 0
2c+2d = 360
2d = 140


d = 140/2 = 70
c = 360-2d/2 = 360-2 · 70/2 = 110
b = 0+c = 0+110 = 110
a = 0+d = 0+70 = 70

a = 70
b = 110
c = 110
d = 70

Our linear equations calculator calculates it.



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