## collegegirl89 Group Title please help!!!! i need to know the horizontal tangents of sin(25x) and the vertical tangents of cos(25x). I got answers of 0 and pi/25 and 25pi/2 and 75pi/2, but my online hw says that theyre wrong one year ago one year ago

1. richyw

$$f(x)=\cos(25x)$$ has no vertical tangent lines, are you in cartesian coordinates?

2. richyw

for the first one you can just take the derivative and set it equal to zero. so $\frac{d}{dx}(\sin25x)=\cos (25x)\cdot\frac{d}{dx}25x=25\cos (25x)$

3. collegegirl89

yeah the interval is from 0 to 2pi

4. collegegirl89

ahh im confused

5. collegegirl89

i thought that cos(25x), when set equal to 0 yielded pi/50 and 3pi/50