- Frederick William Herschel KH, FRS (/ˈhɜːrʃəl/ HUR-shəl; ‹See Tfd›German: Friedrich Wilhelm Herschel [ˈfʁiːdʁɪç ˈvɪlhɛlm ˈhɛʁʃl̩]; 15 November 1738 – 25 August 1822) was a German-British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline Herschel. Born in the Electorate of Hanover, William Herschel followed his father into the military band of Hanover, before emigrating to Great Britain in 1757 at the age of nineteen.
- Right angle (Wikipedia)
In geometry and trigonometry, a right angle is an angle of exactly 90 degrees or 𝜋/2 radians corresponding to a quarter turn. If a ray is placed so that its endpoint is on a line and the adjacent angles are equal, then they are right angles. The term is a calque of Latin angulus rectus; here rectus means “upright”, referring to the vertical perpendicular to a horizontal base line.
