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Rectangles, squares & right triangles

Basic shapes

Japanese school year: Elementary 2

What you learn

Learn the properties of rectangles, squares, and right triangles by focusing on side lengths and right angles. These concepts are useful for recognizing shapes in everyday objects like paper, screens, and tiles. Prior familiarity with straight lines, vertices, and measuring lengths using a ruler will support smooth and confident learning.

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Key points

This formula shows a feature of a rectangle. All four corners (angles A, B, C, D) are right angles (90°).

∠A=∠B=∠C=∠D=90∘\angle A = \angle B = \angle C = \angle D = 90^\circ

This formula shows a feature of a square. All four sides a, b, c, and d have the same length.

a=b=c=da = b = c = d

This formula finds angles in a right triangle. When angle C is 90°, the other two angles A and B add up to 90°.

∠A+∠B=90∘(∠C=90∘)\angle A + \angle B = 90^\circ \quad (\angle C = 90^\circ)

This formula shows how the sides of a right triangle connect. Multiplying sides a and b by themselves and adding them equals side c multiplied by itself.

a2+b2=c2(∠C=90∘)a^2 + b^2 = c^2 \quad (\angle C = 90^\circ)

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