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Right Triangle

  • right triangle 1ARight triangle (a two-dimensional figure) has one side a right 90° interior angle.
  • The other two angles are unequal and no sides are equal.
  • Angle bisector of a right triangle is a line that splits an angle into two equal angles.
  • Circumcircle is a circle that passes through all the vertices of a two-dimensional figure.
  • Height of a right triangle is the length of the two sides and the perpendicular height of the 90 degree angle.
  • Hypotenuse of a right triangle is the longest side or the side opposite the right angle.
  • Inscribed circle is the largest circle possible that can fit on the inside of a two-dimensional figure.
  • Median of a right triangle is a line segment from a vertex (coiner point) to the midpoint of the opposite side.
  • Semiperimeter is one half of the perimeter.
  • 3 edges
  • 3 vertexs
  • a = opposite leg
  • b = adjacent leg
  • c = hypotenuse
  • Angles:  ∠A, ∠B, ∠C
  • Height:  \(h_a\), \(h_b\), \(h_c\)
  • Median:  \(m_a\), \(m_b\), \(m_c\)  -  A line segment from a vertex (coiner point) to the midpoint of the opposite side
  • Angle bisectors:  \(t_a\), \(t_b\), \(t_c\)  -  A line that splits an angle into two equal angles

right triangle 5h a

right triangle 5m a

right triangle 5t a

right triangle 2A

 

 

 

 

 

 

 

Angle bisector of a Right Triangle formulas

\( t_a \;=\;  2 \cdot b \cdot c \cdot  cos \left(  \dfrac{  \dfrac{A}{2}  }{ b + c }  \right)  \) 

\( t_a \;=\;  \sqrt{  b\cdot c \cdot  \dfrac{ 1 - a^2  }{ \left(  b + c \right)^2 }  } \) 

\( t_b \;=\;  2\cdot a\cdot c \cdot   cos \left( \dfrac{  \dfrac{B}{2}  }{ a + c }  \right) \) 

\( t_b \;=\;  \sqrt{  a\cdot c \cdot  \dfrac{ 1 - b^2  }{ \left(  a + c \right)^2 }  } \)

\( t_c \;=\;  a\cdot b \cdot \sqrt{  \dfrac{ 2 }{ a + b }   } \)

Symbol English Metric
\(\large{ t_a, t_b, t_c }\) = angle bisector \(\large{ in}\) \(\large{ mm}\)
\(\large{ A, B, C }\) = angle \(\large{deg}\) \(\large{rad}\)
\(\large{ a, b, c }\) = edge \(\large{ in}\) \(\large{ mm }\)

 

Area of a Right Triangle formula

\( A_{area} = \dfrac{ a \cdot b }{ 2 } \) 
Symbol English Metric
\(\large{ A_{area} }\) = area \(\large{ in}\) \(\large{ mm}\)
\(\large{ a, b, c }\) = edge \(\large{ in}\) \(\large{ mm }\)

 

Circumcircle of a Right Triangle formulas

\( R \;=\;  \dfrac{ 1 }{ 2 } \cdot  \sqrt {  a^2 + b^2  }  \) 

\( R \;=\;  \dfrac{ H }{ 2 }   \) 

Symbol English Metric
\(\large{ R }\) = outcircle \(\large{ in}\) \(\large{ mm}\)
\(\large{ a, b, c }\) = edge \(\large{ in}\) \(\large{ mm }\)
\(\large{ H }\) = hypotenuse \(\large{ in}\) \(\large{ mm }\)

 

Height of a Right Triangle formulas

\( h_a \;=\; b \) 

\( h_b \;=\; a \) 

\( h_c \;=\;  \dfrac{ a \cdot b }{ c} \) 

Symbol English Metric
\(\large{ h_a, h_b, h_c }\) = hight \(\large{ in}\) \(\large{ mm}\)
\(\large{ a, b, c }\) = edge \(\large{ in}\) \(\large{ mm }\)

 

Hypotenuse of a Right Triangle formula

\( c \;=\; \sqrt{ a^2 + b^2}  \) 
Symbol English Metric
\(\large{ c }\) = hypotenuse (H) \(\large{ in}\) \(\large{ mm}\)
\(\large{ a, b, c }\) = edge \(\large{ in}\) \(\large{ mm }\)

 

Inscribed Circle of a Right Triangle formulas

\( r \;=\;   \dfrac{ a\cdot b  }{ a + b + c }   \) 

\( r \;=\;   \dfrac{ a + b - c }{ 2  }   \) 

Symbol English Metric
\(\large{ r }\) = incircle \(\large{ in}\) \(\large{ mm}\)
\(\large{ a, b, c }\) = edge \(\large{ in}\) \(\large{ mm }\)

 

Median of a Right Triangle formulas

\( m_a \;=\;  \sqrt{  \dfrac{ 4\cdot b^2 + a^2 }{ 2 }   }   \) 

\( m_b \;=\;  \sqrt{  \dfrac{ 4\cdot a^2 + b^2 }{ 2 }   }   \) 

\( m_c \;=\;  \dfrac{c }{ 2} \) 

Symbol English Metric
\(\large{ m_a, m_b, m_c }\) = median \(\large{ in}\) \(\large{ mm}\)
\(\large{ a, b, c }\) = edge \(\large{ in}\) \(\large{ mm }\)

 

Perimeter of a Right Triangle formulas

\( P \;=\; a + b + c \) 

\( P \;=\;  a + b +  \sqrt{a^2 + b^2 } \) 

Symbol English Metric
\(\large{ P }\) = perimeter \(\large{ in}\) \(\large{ mm}\)
\(\large{ a, b, c }\) = edge \(\large{ in}\) \(\large{ mm }\)

 

Semiperimeter of a Right Triangle formula

\( s \;=\;   \dfrac{ a + b + c }{ 2  }   \) 
Symbol English Metric
\(\large{ s }\) = semiperimeter \(\large{ in}\) \(\large{ mm}\)
\(\large{ a, b, c }\) = edge \(\large{ in}\) \(\large{ mm }\)

 

Trig Functions

Find A
  • given a c :  \(\; sin( A) \;=\;   \dfrac{ a }{ c }\)
  • given b c :  \(\; cos( A) \;=\;   \dfrac{ b }{ c }\)
  • given a b :  \(\; tan( A) \;=\;   \dfrac{ a }{ b }\)
Find B
  • given a c :  \(\; sin( B) \;=\;  \dfrac{ a }{ c }\)
  • given b c :  \(\; cos( B) \;=\; \dfrac{  b }{ c }\)
  • given a b :  \(\; tan( B) \;=\;  \dfrac{ b }{ a }\)
Find a
  • given A c :  \(\; a \;=\;  c \cdot sin( A) \)
  • given A b :  \(\; a \;=\;  b \cdot tan( A) \)
Find b
  • given A c :  \(\; b \;=\;  c \cdot cos( A) \)
  • given A a :  \(\; b \;=\;  \dfrac{ a }{ tan( A) }\)
Find c
  • given A a :  \(\; c \;=\;   \dfrac{ a }{ sin( A) }\)
  • given A b :  \(\; c \;=\;   \dfrac{ b }{ cos( A) }\)
  • given a b :  \(\; c \;=\;   \sqrt{ a^2 + b^2 } \)
Find Area
  • given a b :  \(\; Area \;=\;  \dfrac{ a\cdot b }{ 2 }\)

 

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