Question 6
(BEL 6) Evaluate $(\cos(\pi/4)+i\sin(\pi/4))^{10}$ in two different ways and prove that
$$\binom{10}1-\binom{10}3+\frac12\binom{10}5=2^4.$$
$$\binom{10}1-\binom{10}3+\frac12\binom{10}5=2^4.$$
IMO 1969 - Longlist Problems Question 6
IMO Shortlist · IMO 1969 - Longlist Problems