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11 Jun 2020
Proof Let s(x) and c(x) be two functions satisfying s’(x) = c(x) and c’(x)=-s(x) for all x. If s(0) = 0 and c(0)=1, prove that [s(x)]2+[c(x)2]=1.
Proof Let s(x) and c(x) be two functions satisfying s’(x) = c(x) and c’(x)=-s(x) for all x. If s(0) = 0 and c(0)=1, prove that [s(x)]2+[c(x)2]=1.
Joram GuingguingLv10
18 Jun 2020
