trigonometry
trigonometry — 名詞
1. a branch of mathematics that studies how the angles and side lengths of triangle
三角學
研究三角形邊角關係的數學
a branch of mathematics that studies how the angles and side lengths of triangles are connected, often used to calculate distances or heights that are difficult to measure directly
Sumin found trigonometry difficult at first but improved after practising the formulas every day.
Sumin 起初覺得三角學很難，但每天練習公式後進步了。
personal experience + practice collocation
The surveyor used trigonometry to estimate the height of the bridge across the river.
測量員利用三角學來估算橋樑橫跨河面的高度。
used + noun to [verb] — purpose structure
In trigonometry class, students learn how to find unknown angles using sine and cosine.
在三角學課堂上，學生學習用正弦和餘弦來計算未知角度。
Without trigonometry, engineers could not design curved bridges or safe highway ramps.
沒有三角學，工程師就無法設計彎曲橋樑或安全的高速公路匝道。
Hassan drew a right-angled triangle to show how trigonometry connects the sides to the angles.
Hassan 畫了一個直角三角形，來說明三角學如何連結三角形邊與角的關係。
用法筆記
Commonly used as an uncountable noun; you study trigonometry as a subject, not 'a trigonometry'. Frequently abbreviated informally to trig in spoken English (e.g., 'I have a trig test tomorrow').