Question

how does 2cos5xsin5x turn into/equal sin10x?

Answer 1

\(\sin(2*x)=2\sin(x)cos(x)\)
so
\(\sin(2*(5x))=2\sin(5x)\cos(5x)\) i.e. \(\sin(10x)=2\sin(5x)\cos(5x)\)

Answer 2

ah... the application of the double angle formula confused me. thank you

Answer 3

i didn't know how to use the double angle formula

Answer 4

think of it anytime you have sin cosin next to each other

for identities anyway....