Make: Geometry

You can’t stretch the triangle and have it stay con-

gruent, though. The congruent triangles are all

ones that could be drawn around the same physi-

cal triangle, which means all the sides and angles

of the triangle have to stay constant.

But you don’t need to know all three sides and all

three angles to say that two triangles are congru-

ent. If you know two angles of a triangle, you know

all three (because they have to add up to 180°, as

we learned in the last section). When you’ve set

the three angles of a triangle, all of the triangles

you can make with those angles will be similar tri-

angles. They will be the same shape, but because

none of ...