There is a rectangle with a height of 8 cm and a square bottom. If you shorten its height by 2 cm, its surface area will be reduced by 40 square cm. Find the volume of the cuboid

There is a rectangle with a height of 8 cm and a square bottom. If you shorten its height by 2 cm, its surface area will be reduced by 40 square cm. Find the volume of the cuboid

40 △ 2 = 20 cm
Side length of the bottom of the cuboid: 20 △ 4 = 5cm
Cuboid volume: 5 × 5 × 8 = 200 cubic centimeter

In △ ABC, a = 7, B = 43, C = 13, then the minimum angle is ()
A. π3B. π6C. π4D. π12

∵ in △ ABC, a = 7, B = 43, C = 13, C is the smallest edge, C is the smallest angle. According to cosine theorem, COSC = A2 + B2 − c22ab = 49 + 48 − 132 × 7 × 43 = 32 ∵ C is the inner angle of triangle, C ∈ (0, π), C = π 6, that is, the smallest angle of △ ABC is π 6

The opposite side of angle ABC, if a = 2, C = π / 4, CoSb = 2 √ 5 / 5, find the area of triangle (find the detailed process)

Inb / 2 = the square of (1 - (CoSb / 2) = the square of (1-4 / 5) = (5) / 5sinb = 2sinb / 2cosb / 2 = 4 / 5cosb = 2 (CoSb / 2) - 1 = 3 / 5sina = sin (B + C) = sinbcosc + cosbsinc = (4 / 5) * ((2) / 2) + (3 / 5) * ((2) / 2) a / Sina = C / sinc