If sin titan=3/5,what is cos titan if titan is an acute angle

Substitute the given value $\sin \theta = \frac{3}{5}$ into the identity.

$$\left(\frac{3}{5}\right)^2 + \cos^2 \theta = 1$$

$$\cos^2 \theta = 1 - \frac{9}{25}$$ $$\cos^2 \theta = \frac{25}{25} - \frac{9}{25}$$ $$\cos^2 \theta = \frac{16}{25}$$

$$\cos \theta = \pm\sqrt{\frac{16}{25}}$$ $$\cos \theta = \pm\frac{4}{5}$$

Since $\theta$ is an acute angle, it lies in the first quadrant ($0^\circ < \theta < 90^\circ$). In the first quadrant, both sine and cosine values are positive.
Therefore, $\cos \theta$ must be positive.

$$\cos \theta = \frac{4}{5}$$

The value of $\cos \theta$ is $\boxed{\frac{4}{5}}$.