Solution 2.2:9a

From Förberedande kurs i matematik 1

We can start by drawing the points 14 , 33  and 10  in a coordinate system and draw lines between them, so that we get a picture of how thetriangle looks.

If we now think of how we should use the fact that the area of a triangle is given by the formula

Area= 21 (base)∙(height),

it is clear that it is most appropriate to use the edge from 10  to 14  as the base of the triangle. The base is then parallel with the y-axis and we can read off its length as the difference in the

y -coordinate between the corner points 10  and 14 , i.e.

base =4−0=0. In addition, the triangle's height is the horizontal distance from the third corner point 33  to the base and we can read that off as the difference in the x -direction between 33  and the line x=1, i.e.

height =3−1=2.

Thus, the triangle's area is

Area= 21 (base)∙(height) \displaystyle =\frac{1}{2}\centerdot 4\centerdot 2=4 = area units.