# 4.3 | Right Triangle Trigonometry

Let $$\theta$$ be an acute angle $$(0 < \theta < \pi/2)$$ of a right triangle. The six basic trigonometric functions are defined as follows:
• $$\displaystyle \sin \theta = \frac{opp}{hyp}$$
• $$\displaystyle \csc \theta = \frac{hyp}{opp}$$
• $$\displaystyle \cos \theta = \frac{adj}{hyp}$$
• $$\displaystyle \sec \theta = \frac{hyp}{adj}$$
• $$\displaystyle \tan \theta = \frac{opp}{adj}$$
• $$\displaystyle \cot \theta = \frac{adj}{opp}$$

where $$opp$$ is the length of the side opposite $$\theta$$, $$adj$$ is the length of the side adjacent to $$\theta$$ and sharing the right angle, and $$hyp$$ is the length of the hypotenuse (the side opposite the right angle).