Sources:
Visual - various maths sites (credits to original creator)
Questions - Dong Zong's Textbook
suitable for SUEC (Maths), SPM (Maths and Add Maths) too
22. 𝒑𝒈 𝟐𝟐𝟗 − 𝟐𝟑𝟎
𝑟 =
∆
𝑠
inscribed circle in a triangle, r 三角形旳内切圆半径
23. 𝒑𝒈 𝟐𝟑𝟏 − 𝟐𝟑𝟐
𝑟 =
∆
𝑠
=
84
21
= 4
inscribed circle in a triangle, r 三角形旳内切圆半径
Editor's Notes
The picture on the right is a schematic diagram of the crank connecting rod structure. When the crank OA is at the left horizontal position OB, the position of the connecting rod end point P is at Q.
Rú yòu tú, jiǎ chuán zài hé dǎo B dì zhèng nánfāng A chù, yǐ 4 hǎilǐ/xiǎoshí dì sùdù xiàng zhèng běi fāngxiàng hángxíng, qiě A dào B dì jùlí wèi 12 hǎilǐ; tóngshí, yǐ chuán yǐ 6 hǎilǐ/xiǎoshí dì sùdù qiě B dǎo chūfā, xiàng dǎo dì běi piān xī 60 degree dì fāngxiàng shǐ qù, wèn 2 xiǎoshí hòu, liǎng chuán xiāngjù duōshǎo hǎilǐ?
As shown in the picture on the right, ship A is sailing at a speed of 4 nautical miles/hour to the true north at A, just south of Island B, and the distance from A to B is 12 nautical miles; meanwhile, ship B is traveling at a speed of 6 nautical miles/hour. And depart from Island B and head towards 60 degrees west of the island. After 2 hours, how many nautical miles are the two boats apart?
In the 325 degree direction, there are three points A, B and C, AB = 7 km on the road, and one point D to the south of A, AD = 8 km, AC = 17 km, find C to D bearing, BD distance.
One observer at the top of the cliff above the sea level h meter, the depression angles of the two boats that stop at the sea surface are 29 degrees and 48 degrees, and the line of the two boats is perpendicular to the cliff. Boat distance = 100 meter, find h.
http://getdrawings.com/get-drawing#angle-of-elevation-and-depression-problems-with-solutions-and-drawing-60.jpg