An isosceles triangle is one that has two equal sides and two equal angles. In certain cases, you will have to design it based on limited information. If you already know the value of lengths, base and height, it is possible to go forward with just a ruler and a compass (or even just with a compass, if the problem mentions straight segments). With a protractor, you can use angle information to draw the isosceles triangle.

## Steps

### Method 1 of 4: All Sides Known

#### Step 1. Assess what you know

In this method, you must know the length of the base of the triangle and the length of the two equal sides. You can also use this method if you are given line segments that are representative of the base and sides rather than precise measurements.

- In an example, you might know that the base of a triangle is 8 cm long{displaystyle 8 {text{cm}}}
e seus lados iguais, de 6 cm{displaystyle 6 {text{cm}}}

, ou ter duas linhas, uma representando a base e outra representando os dois lados.

#### Step 2. Make the foundation

Use a ruler so that the line is accurately measured. For example, if the base has a length of 8 cm{displaystyle 8 {text{cm}}}

, use um lápis e uma régua para fazer uma reta com essa medida exata.

### Se você tem um segmento de reta no lugar de uma medida, faça a base ajustando o compasso no valor desejado. Faça um ponto final e use-o para marcar a outra extremidade. Conecte ambos os pontos com um escalímetro ou uma régua

#### Step 3. Adjust the time signature

To do this, open it to equal sides width. If the problem defines a measure, use a ruler. If you know a straight segment, adjust the compass filling the entire length.

- If the side lengths measure 6 cm{displaystyle 6 {text{cm}}}
, por exemplo, abra o compasso nesse valor. Ou, ainda, se você tem o valor de um segmento de reta, ajuste-o no comprimento dado.

#### Step 4. Draw an arc over the base

To do this, place the end of the compass at one end. Pass the graphite through the space on the base, drawing an arc.

### It should advance to at least half the length of the base

#### Step 5. Draw an arc crossing the other over the base

Without changing the bar width, place the graphite at the other end. Draw an arc that crosses the first one.

#### Step 6. Draw the sides of the triangle

Use a ruler to draw lines that connect the intersection point of the arcs with the ends of the base. The resulting figure will be an isosceles triangle.

### Method 2 of 4: Two Sides and the Angle Between Them Known

#### Step 1. Assess what you know

In this method, you must know the length of the two equal sides and the value of the angle between them. You can also use it if you have a straight line segment representative of the size in hand instead of an exact measurement.

- In an example, you might know that the isosceles triangle has two equal sides of 7 cm{displaystyle 7 {text{cm}}}
ou mesmo um segmento de reta representando esse tamanho. Você também pode saber que o ângulo entre eles equivale a 50{displaystyle 50}

.^{°}

#### Step 2. Draw the angle

Use a protractor to construct the angle from the quoted measurement. Each of the vectors must be larger than the desired size.

- You may need to angle 50{displaystyle 50}
, por exemplo. Uma vez que os lados do triângulo medem 7 cm{displaystyle 7 {text{cm}}}^{°}, os vetores devem ser ligeiramente maiores. Você pode usar uma régua ou o próprio compasso para determinar um comprimento adequado.

#### Step 3. Adjust the time signature

If you know the size of the sides, use a ruler to open the compass to the desired size. If you have a straight line segment at hand, rather than an exact measure, use it to adjust the time signature as needed.

- For example, if the sides measure 7 cm{displaystyle 7 {text{cm}}}
, use uma régua para abrir o compasso nesse mesma medida.

#### Step 4. Draw an arc

To do this, place the end of the compass at the vertex of the angle (where both vectors meet). Draw a long arc that crosses each of your vectors - you can also draw two small arcs at these crossovers.

#### Step 5. Draw the base

Using a ruler or a caliper, draw a line connecting the points where the arc intersects the two vectors. The resulting figure is an isosceles triangle.

### Method 3 of 4: Base and Known Adjacent Angles

#### Step 1. Assess what you know

In this method, you must know the length of the base or the value of a line segment representative of the base. You should also know the measurement of the two angles adjacent to it, remembering that in an isosceles triangle they will both be equal.

- For example, the base 9 cm isosceles triangle{displaystyle 9 {text{cm}}}
terá dois ângulos adjacentes de 45{displaystyle 45}

.^{°}

#### Step 2. Draw the base

If you know the base measurement, use a ruler to make it the proper length. Accurately measure and then create a straight line.

### You can still draw the base by adjusting the compass to the distance of the line segment. When marking one end, mark the other with the same instrument and then use a ruler or a scale to connect the two points

#### Step 3. Make the first angle

Use a protractor to draw the angle on the left side of the base. The vector should advance a little beyond the half of the base, crossing the other side of the triangle.

#### Step 4. Draw the second angle

Use the protractor to angle the right side of the base. The second vector must cross the first, forming the apex of the triangle. The resulting figure will be an isosceles triangle.

### Method 4 of 4: Known Base and Height

#### Step 1. Assess what you know

In this method, you need to know the length of the triangle's base as well as its height. You can also use it if you have line segments representing base and height instead of precise measurements.

- For example, you might have a base 5 cm isosceles triangle{displaystyle 5 {text{cm}}}
e altura 2, 5 cm{displaystyle 2, 5 {text{cm}}}

#### Step 2. Draw the base

If you know the measurement value, use a ruler. If the base has 5 cm{displaystyle 5 {text{cm}}}

de comprimento, faça uma reta com essa dimensão com o auxílio de um escalímetro ou uma régua.

### Ao trabalhar com um segmento de reta em vez de uma medida precisa, faça a base ajustando o compasso para que tenha a largura da base. Desenhe um ponto na extremidade e use o compasso para desenhar o segundo. A seguir, conecte-os com um escalímetro ou uma régua

#### Step 3. Draw a line dividing the base

In other words, make a line that crosses the first one in half. It is possible to use a compass in the method described here. Draw the line with a size at least equal to the height of the triangle.

- You can also use a ruler and protractor to split the line. Divide the base length in half and use the ruler to make a midpoint. Then, with the help of a protractor, make a straight over it that crosses the base at an angle of 90{displaystyle 90}
.^{°}

#### Step 4. Adjust the time signature

If you know the measurement of the triangle's height, use a ruler to open the compass to the desired size (eg 2.5 cm{displaystyle 2, 5 {text{cm}}}

). Caso esteja trabalhando com um segmento de reta, abra-o no comprimento da linha mencionada.

#### Step 5. Draw an arc over the height

Place the end of the compass at the midpoint of the base and make an arc across the upper bisector. You need to draw the arc on only one side of the base.

#### Step 6. Draw the triangle

Connect the point where the height and arc intersect at both ends of the base. The resulting figure will be an isosceles triangle.