### Telescoping Series

Find $S_r = 1^r + 2^r + 3^r + ... + n^r$ where r is any fixed positive integer in terms of $S_1, S_2, ... S_{r-1}$.

### Degree Ceremony

What does Pythagoras' Theorem tell you about these angles: 90°, (45+x)° and (45-x)° in a triangle?

### OK! Now Prove It

Make a conjecture about the sum of the squares of the odd positive integers. Can you prove it?

# Harmonically

##### Stage: 5 Challenge Level:

(a) Is it true that a large value of $n$ can be found such that: $$S_n = 1 +{1\over 2} + {1\over 3} + {1\over 4} + ... + {1\over n} > 100?$$

(b) By considering the area under the graph of $y = {1\over x}$ between $a ={1\over n}$ and $b = {1\over n-1}$ show that this series grows like $\log n$.