Geometry Strategy Guide / Chapter 9 / exercise 5 / page 243

[antonia.vouraki]

Hi,

I have trouble with exercise 5 on the Geometry Strategy Guide / Chapter 9 / page 243.

Answer for ex. 5 Choice B: I don't understand the reasoning of the explanation why the height of triangle CDF and DEF is the same.

Because if we say that they have same base and share vertex F but we don't know if vertex F (FD) is perpendicular to the base in order to say that the height is the same. Then I can't think of how the explanation given concludes on the fact that the height is the same.

Could you please help?

Many thanks!!

[tommywallach]

Heights of triangles are always perpendicular to the base--that's the definition of a triangle's height: a line drawn from the apex (highest point) of the triangle that meets the base or the extension of the base at a right angle. Does that clarify things?

-t