# Right Trapezoid

Written by Jerry Ratzlaff on . Posted in Plane Geometry

• Right trapezoid (a two-dimensional figure) is a trapezoid with only one pair of parallel edges and two adjacent right angles.
• Acute angle is an angle that measures less than 90°.
• Obtuse angle is an angle that measures more than 90°.
• a & c are bases
• b & d are legs
• a ∥ c
• a ≠ c
• b ≠ d
• ∠A < 90°
• ∠B > 90°
• ∠C = ∠D
• ∠A + ∠B = 180°
• ∠C + ∠D = 180°

### Angle of a Right Trapezoid Formula

$$\large{ x = 90° - arccos \; \frac{ d^2 + b^2 - \left(a-c \right)^2 }{ 2\;d\;b } }$$

$$\large{ y = 180° - x }$$

Where:

$$\large{ x }$$ = acute angle

$$\large{ y }$$ = obtuse angle

$$\large{ a, b, c, d }$$ = edge

### Area of a Right Trapezoid formula

$$\large{ A_{area} = \frac{1}{2} \; d \; \left( a + c \right) }$$

Where:

$$\large{ A_{area} }$$ = area

$$\large{ a, b, c, d }$$ = edge

### Diagonal of a Trapezoid Formula

$$\large{ d' = \sqrt{c^2+d^2} }$$

$$\large{ D' = \sqrt{a^2+d^2} }$$

Where:

$$\large{ d', D' }$$ = diagonal

$$\large{ a, b, c, d }$$ = edge

### Midline of a Right Trapezoid formula

$$\large{ m = \frac{a+c}{2} }$$

Where:

$$\large{ m }$$ = midline

$$\large{ a, b, c, d }$$ = edge

### Perimeter of a Trapezoid formula

$$\large{ P = a + b + c + d }$$

Where:

$$\large{ P }$$ = perimeter

$$\large{ a, b, c, d }$$ = edge

### Side of a Right Trapezoid Formula

$$\large{ b = \sqrt{ \left( a-c \right)^2 + d^2 } }$$

$$\large{ d = \sqrt{ b^2 - \left( a-c \right)^2 } }$$

Where:

$$\large{ b, d }$$ = edge

$$\large{ a, c }$$ = edge