Trigonometry — Chapter Summary

In a right triangle

In a right triangle, sinθ = opposite side / hypotenuse, cosθ = adjacent side / hypotenuse, and tanθ = opposite side / adjacent side. In the standard t

cosecθ = 1/sinθ

cosecθ = 1/sinθ, secθ = 1/cosθ, and cotθ = 1/tanθ = cosθ/sinθ. Also, sinθ × cosecθ = 1, cosθ × secθ = 1, and tanθ × cotθ = 1.

From the Pythagoras theorem in

From the Pythagoras theorem in a right triangle, BC² + AB² = AC². Dividing by AC² gives sin²θ + cos²θ = 1. Dividing this identity by sin²θ gives 1 + c

The key values for acute

The key values for acute and special angles are: sin 0° = 0, sin 30° = 1/2, sin 45° = 1/√2, sin 60° = √3/2, and sin 90° = 1. Also, tan 90° is not defi

If an observer looks at

If an observer looks at a point above the horizontal line, the angle formed is the angle of elevation. If the observer looks at a point below the hori