The values for the expressions are:
- \( \cos(75^\circ) \approx 0.2588 \)
- \( \tan\left(-\frac{\pi}{8}\right) \approx -0.4142 \)
- \( \tan\left(\frac{\pi}{12}\right) \approx 0.2679 \)
- \( \sin\left(\frac{3\pi}{8}\right) \approx 0.9239 \)
- \( \tan(67.5^\circ) \approx 2.4142 \)
- \( 10 \cdot \cos(67.5^\circ) \approx 3.8268 \)
Thus, the final boxed answers are:
\[
\boxed{\cos(75^\circ) \approx 0.2588}
\]
\[
\boxed{\tan\left(-\frac{\pi}{8}\right) \approx -0.4142}
\]
\[
\boxed{\tan\left(\frac{\pi}{12}\right) \approx 0.2679}
\]