QuickenBrain

Choose a triangle ratio

Identify opposite, adjacent and hypotenuse before using sine, cosine or tangent.

Name sides relative to the angle

In a right triangle, the hypotenuse is opposite the right angle. For an acute angle θ, the opposite side lies across from θ. The adjacent side touches θ and is not the hypotenuse.

The ratios are sin θ = opposite/hypotenuse, cos θ = adjacent/hypotenuse and tan θ = opposite/adjacent. In this 3–4–5 triangle, sin θ = 3/5, cos θ = 4/5 and tan θ = 3/4.

345θ
The side opposite θ is 3; the adjacent leg is 4.

Read the rest as a member

You are reading the opening. Members read every lesson and guide in full. A free account reads the first lesson in each subject in full.

You are reading the opening. Your free account reads the first lesson in each subject in full. Members read every lesson and guide in full.

First lesson in this subject: Complete the angle sum

View membership
Have an account? Sign in here.

By signing in or requesting a code, you confirm you are 13 or older and agree to the terms. See how we use your information in our privacy page.

The code lasts ten minutes and works once.