01 76 38 08 47
Kartable logo
HomeBrowseSearchLog in

To enjoy 10 free documents.

Kartable logo
HomeBrowseSearchLog in

To enjoy 10 free documents.

  1. Home
  2. 12th grade
  3. Geometry
  4. Exercise : Use properties of special triangles to determine lengths, angles, heights

Use properties of special triangles to determine lengths, angles, heights Geometry

Use the properties of the following special triangle to determine a.

-

We know that:

\widehat{A} + \widehat{B}+ \widehat{C} = 180^\circ

30^\circ + 75^\circ+ \widehat{C} = 180^\circ

\widehat{C} = 75^\circ

Therefore:

\widehat{B} = \widehat{C}

This is an isosceles triangle and we have:

AC = AB = 5

a=5

Use the properties of the following special triangle to determine a.

-

We have:

\widehat{B} = \widehat{C}

This is an isosceles triangle so point H is the midpoint of BC. Therefore:

BH=2

Using the Pythagoras theorem, we find:

a=\sqrt{5^2+2^2}= \sqrt{29}

a= \sqrt{29}

Use the properties of the following special triangle to determine a.

-

We have:

AC = AB

This is an isosceles triangle and:

\widehat{B} = \widehat{C}

We know that:

\widehat{A} + \widehat{B}+ \widehat{C} = 180^\circ

80^\circ+ 2\widehat{B} = 180^\circ

\widehat{B} = 50^\circ

\widehat{a}=50^\circ

Use the properties of the following special triangle to determine a.

-

We have:

AC = AB

This is an isosceles triangle and:

\widehat{B} = \widehat{C}

We know that:

\widehat{A} + \widehat{B}+ \widehat{C} = 180^\circ

60^\circ + \widehat{2 C} = 180^\circ

\widehat{C} = 60^\circ

This is also an equilateral triangle. So:

BC = 4

a=4

Use the properties of the following special triangle to determine a.

-

Using the Pythagoras theorem, we find:

\left(BA\right)^2=\left(AH\right)^2+\left(HB\right)^2

\left(AH\right)^2=\left({BA}\right)^2-\left(BH\right)^2

\left(AH\right)^2=\sqrt{80}^2-4^2 =64

Using the Pythagoras theorem, we find:

\left(AC\right)^2=\left(AH\right)^2+\left(HC\right)^2

\left(HC\right)^2=\left({AC}\right)^2-\left(AH\right)^2

\left(HC\right)^2=\sqrt{320}^2-64 =256

Therefore:

HC=16

a=16

Use the properties of the following special triangle to determine a.

-

We have:

AC = AB

This is an isosceles triangle and:

\widehat{B} = \widehat{C}

We know that:

\widehat{A} + \widehat{B}+ \widehat{C} = 180^\circ

50^\circ +2 \widehat{C} = 180^\circ

\widehat{C} = 65^\circ

\widehat{a} = 65^\circ

Use the properties of the following special triangle to determine a.

-

We know that:

\widehat{A} + \widehat{B}+ \widehat{C} = 180^\circ

Since the triangle is isosceles, we have:

\widehat{B} = \widehat{C}

90^\circ + 2\widehat{C} = 180^\circ

\widehat{C} = 45^\circ

\widehat{a} = 45^\circ

The editorial charter guarantees the compliance of the content with the official National Education curricula. Learn more

The courses and exercises are written by the Kartable editorial team, made up of teachers certified and accredited. Learn more

See also
  • Course : Triangles
  • Exercise : Use the law of cosine to determine lengths and angles
  • Exercise : Find the area of a triangle
  • Exercise : Identify special triangles
  • Exercise : Use congruence to determine measures
  • Exercise : Complete proofs involving triangles
  • support@kartable.com
  • Legal notice

© Kartable 2026