Rectangular area:1.2×1.5 =1.8 (square meter)
Semicircular area: 3.14× (1.2/2 )× (1.2/2) ÷ 2 = 0.5652 (square meter).
Graphic area: 1.8+0.5652=2.3652 m2.
Figure 2: Calculate the area of the big circle first, then calculate the area of the shadow part with "the ratio of the blank part to the shadow part of the big circle is 4: 1", and then calculate the area of the small circle with "the ratio of the blank part to the shadow part of the small circle is 3: 2".
Great circle area: 3.14×10×10 = 314 (square centimeter)
Shadow area: 314×1(4+1) = 62.8 (square centimeter)
Small circle area: 62.8÷2/(3+2)= 157 (square centimeter)
Figure 3: 1. Perimeter: half of the circumference of a big circle+half of the circumference of a small circle+diameter of a big circle.
Half of the circumference of the great circle: 3.14× 2× (2+3) ÷ 2 =15.7 cm.
Half of the circumference of a small circle: 3. 14×2×2= 12.56 cm.
Diameter of great circle: (2+3)×2= 10 cm.
Graphic perimeter:15.7+12.56+10 = 38.26 cm.
Graphic area: It is a semicircle. First calculate the radius of the outer circle (2+3) cm, then calculate the area of the circle, and then divide by 2.
The radius of the excircle is: 2+3 = 5cm.
Ring area: 3.14× (5× 5-2× 2) = 65.94cm2.
Shadow area: 65.94÷2=32.97 square centimeters.
Figure 4: Shadow perimeter = sum of two sides of a square +65438+ 0 of the perimeter of a circle with a radius of 4cm.
The sum of two sides of a square is: 4+4 = 8 cm.
The circumference 1 of a circle with a radius of 4 cm is: 3.14× 2× 4×1/4 = 6.28 cm.
Circumference of shaded part: 8+6.28 =14.28cm.
Shadow area = square area-the area of a circle with a radius of 4cm 1.
Square area: 4×4= 16 cm2.
The area 1 of a circle with a radius of 4cm is: 3.14× 4×1/4 =12.56cm2.
Shadow area:16-12.56 = 3.44cm2.