1819 H2Y §3.1

• Wiskunde
• Middelbare school
• havo
• Leerjaar 2

Enclosing an area

(You will need this for exercise 4)

Square roots

If I have a square with an area of

9 cm2, I know the length of the

sides are 3 cm, because

If the area of a square is 16 cm2,

the length of the sides are 4 cm, because

Square roots

What if I have a square with an area of 156.25 cm2?

After trying some numbers I can find that the

sides are 12.5 cm, because

To find the length of the sides without trying a lot

of different numbers, you can use the square root.

Square roots

The square root of 25 is 5, because the square of 5 is 25.

The square root of 6.25 is 2.5, because the square of 2.5 is 6.25

There is no square root of -16 (or any other negative number), because there is no number I can square to get a negative result

Exact or Approximation

Some square roots give a whole number. For example:

Exact or Approximation

Some square roots do not give a whole number.

If you calculate the square root of 15 on your calculator, you get

It makes sense that the square root of 15 lies between 3 and 4, because 15 lies between 9 and 16 and the square root of 9 is 3 and the square root of 16 is 4.

Exact or Approximation

If we want to know the lenght of the sides of a square with an area of 15 cm2,

we say that the exact length of the sides is

we say that the length of the sides is approximately 3.87

Opposite numbers

Which theories/homework exercises should I discuss on the board?

Homework Friday

Make and correct the exercises of §3.1 of your chosen path (support, standard, challenge)