## -Welp- one year ago I am having trouble figuring out when to use SAS, SSS, ASA and AS postulates. Examples: http://i.imgur.com/uP4xP7P.png I can see how SSS or SAS could be the answer but I don't know which one I'm supposed to use. http://i.imgur.com/czkBNRh.png I don't know if I should use SSS, SAS, or AS.

1. anonymous

to find the postulates youll need to now th hl postulate and the la postulates

2. phi

You use SAS, SSS, etc to show two triangles are congruent (same size and shape, i.e. identical) But this problem has two triangles that are *not* congruent. The two triangles are similar (their corresponding angles are equal)

3. phi

thus you could use "corresponding parts of similar triangles" to write a ratio of the sides of the little triangle and the "big" outer triangle. For example, the ratio of left side to bottom side the small triangle has 5 for the left and 10 for the bottom the big triangle has left side 5+2.5= 7.5 and x (unknown) for the bottom write the ratio $\frac{10}{5} = \frac{x}{7.5}$ simplify the left ratio to 2 $2= \frac{x}{7.5}$

4. phi

multiply both sides by 7.5 to get 2*7.5 = x or x= 15 in other words, the bottom side of the big triangle is 15