📐 Intro to trigonometry

Unit 3 · Numbers & functions · 10 min

In a right triangle: sin A = opposite/hypotenuse, cos A = adjacent/hypotenuse, tan A = opposite/adjacent (SOH-CAH-TOA). sin 30° = 0.5. Engineers use them for slopes, heights and distances.

Words in this lesson

• 斜边 (xié biān) — hypotenuse
• 角度 (jiǎo dù) — angle

Project: Estimate a tree's or building's height with a protractor and tape; write out your working.