- Right angle (Wikipedia)
In geometry and trigonometry, a right angle is an angle of exactly 90 degrees or đ/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.
- Indian Ocean (Wikipedia)
The Indian Ocean is the third-largest of the world’s five oceanic divisions, covering 70,560,000 km2 (27,240,000 sq mi) or approx. 20% of the water on Earth’s surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by the Southern Ocean, or Antarctica, depending on the definition in use. Along its core, the Indian Ocean has large marginal, or regional seas, such as the Andaman Sea, the Arabian Sea, the Bay of Bengal, and the Laccadive Sea.
