## 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 Group Title

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

2. richyw Group Title

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 Group Title

yeah the interval is from 0 to 2pi

4. collegegirl89 Group Title

ahh im confused

5. collegegirl89 Group Title

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