How do you find critical points for the equation $(\frac{7}{10}) cos (\frac{x}{10})$ $(7/10)cos(x/10)$ ?

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Answer 1 · 2018-06-25T05:25:14

$x = 10 k π$ $x=10kpi$ where $k$ $k$ is an integer.

$f (x) = \frac{7}{10} cos (\frac{x}{10})$ $f(x)=7/10cos(x/10)$

Critical points are when derivative is 0 or undefined.

$f'(x)=-7/100sin(x/10)$

Sin is well defined at every point but is equal to zero at 0, $pi$

$-7/100sin(x/10)=0$

#sin(x/10)=0

$sin(y)=0$ at $y=kpi$

Therefore

$sin(x/10)=0$ at $x/10=kpi$ so $x=10kpi$ where $k$ in an integer.

How do you find critical points for the equation (7/10)cos(x/10)(710)cos(x10)(7/10)cos(x/10)?