#### Angel

##### she/her/they nonbinary transfem

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f and g are functions of Domain = R defined respectively by

f(x) = 1 - cos(3x) and g(x) = sin(3x)

a is a real number, belonging to the interval ] pi/3 , pi/2 [

consider r and s such as

r is tangent to the f function graphic, in the point of absciss a

s is tangent to the g function graphic, in the point of abciss a + pi/6

It is known that r and s are perpendicular

Prove that sen(3a) = -(1/3)

@Gr4Ss