PLEASE. NEED HELP. Find the sum.

Distribute the sum:

Use the following formulas:

In case you don't know where those formulas came from:

The first one is obvious; you're just adding n copies of 1, so 1 + 1 + ... + 1 = n.

The second can be proved in this way: let S be the sum 1 + 2 + 3 + ... + n. Rearrange it as S = n + (n - 1) + (n - 2) + ... + 1. Then 2S = (n + 1) + (n + 1) + (n + 1) + ... + (n + 1), or n copies of n + 1. So 2S = n(n + 1). Divide both sides by 2 and we're done.

we don't have enough info to solve this

central angle of a triangle has the same measure as its intercepted arc.

step-by-step explanation: