Wendy described four triangles as shown below:
triangle a: all sides have length 9 cm.
triangle b: two sides have length 10 cm, and the included angle measures 60°. triangle c: two angles measure 50°.
triangle d: base has length 8 cm, and base angles measure 45°.

which triangle is not a unique triangle?

When angles are the only specification, one side can be any length you want. The triangle is not uniquely specified by its angles.

The appropriate choice is ...

... Triangle C: Two angles measure 50°.

step-by-step explanation:

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for