Definition

A mathematical function that relates the angle of a triangle to the lengths of its sides, specifically the ratio of the length of the side next to an angle to the length of the longest side.

Example

In trigonometry, the cosine of a 60-degree angle is 0.5.

Conversation

Have you ever studied the cosine function in math class?

Yeah, I remember it was about the ratios in right triangles.

Right! It really helps to understand how to use the cosine in different problems.

For sure, it's so useful when solving for angles!

Synonyms & Antonyms

Root Explanation

Cosine is formed from "co-" (meaning together) and "sinus" (meaning curve or bay). The term refers to the cosine function, which relates to the sine function in a right triangle, thus representing a relationship between angles and sides together.

Memory Tip

Think of 'together' ('co-') and the 'curve' ('sinus') of a triangle to remember that cosine relates to the sine function in trigonometry.

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