## Algebra and Trigonometry 10th Edition

We know that $\langle u_1,u_2 \rangle \cdot \langle v_1,v_2\rangle$ is equal to $u_1v_1 +u_2v_2$. Thus, we find that the dot product of these two vectors is: $$sin\theta cos\theta -sin\theta cos\theta =0$$ The dot product is zero, so the vectors are orthogonal.