As shown in the figure, in the square ABCD, f is a point on CD, AE ⊥ AF, point E is on the extension line of CB, EF intersects AB at point G, proving: de · FC = BG · EC

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• 1. As shown in the figure, in square ABCD, e is a point on the edge of CD, f is a point on the extension line of BC, CE = CF
• 2. As shown in the figure, in square ABCD, e is a point on CD, f is a point on BC extension line, CE = cf. (1) prove: △ BCE ≌ △ DCF; (2) if ∠ BEC = 60 °, calculate the degree of ∠ EFD
• 3. E is on CD, f is a point on the extension line of BC, CE = CF (1) proves that triangle BCE congruent triangle DCF (2) ∠ FD E is on CD, f is a point on BC extension line, CE = CF (1) Proof of triangle BCE congruent triangle DCF (2) How much is ∠ FDC = 30 ° and ∠ bef = 0
• 4. As shown in the figure, in the isosceles trapezoid ABCD, ad = 4cm, BC = 8cm, e is the midpoint of the waist AB, CE divides the trapezoid circumference into two parts, the difference is 3cm, and calculates the trapezoid circumference
• 5. As shown in the figure, in the isosceles trapezoid ABCD, ad = 4cm, BC = 8cm, e is the midpoint of the waist AB, CE divides the trapezoid circumference into two parts, the difference is 3cm, and calculates the trapezoid circumference
• 6. As shown in the figure, in the isosceles trapezoid ABCD, ad = 4cm, BC = 8cm, e is the midpoint of the waist AB, CE divides the trapezoid circumference into two parts, the difference is 3cm, and calculates the trapezoid circumference
• 7. As shown in the figure, in the isosceles trapezoid ABCD, ad = 4cm, BC = 8cm, e is the midpoint of the waist AB, CE divides the trapezoid circumference into two parts, the difference is 3cm, and calculates the trapezoid circumference
• 8. In the trapezoidal ABCD, ab = 8, ad = 5, CD = 6, BC = 15. Point E is on the bottom BC, and point F is on the waist CD. EF bisects the area and perimeter of ABCD at the same time to find the length of CE
• 9. In the isosceles trapezoid ABCD, AD / / BC, assuming BC = 4, ad = 8, angle a = 45 degrees, the area of the trapezoid is calculated
• 10. As shown in the figure, in the trapezoidal ABCD, ad ‖ BC, ∠ B = 90 °, ab = 14cm, ad = 18cm, BC = 21cm, point P starts from point a, moves at 1cm / s along side ad to point D, and point Q starts from point C, moves at 9cm / s along side CB to point B. If one point moves to the end point, the other point stops. If P and Q start at the same time, can a quadrilateral PQCD become an isosceles trapezoid? If so, how many seconds? If not, please give reasons
• 11. As shown in the figure, the point E is on the diagonal BD of the square ABCD, and be = AB, EF ⊥ BD, EF and CD intersect at the point F to prove de = EF = FC
• 12. As shown in the figure, in square ABCD, e is a point on the edge of BD, and be = BC, EF is perpendicular to BD, intersecting CD with F
• 13. As shown in the figure, take a point E on the diagonal BD of square ABCD, make be = BC, make ef vertical BD, intersect CD with F. the line segment De is equal to EF and FC? Why?
• 14. How to calculate the electricity consumption of refrigerator in an hour What is the formula?
• 15. Suppose that two resistors with resistance values of 1 ohm and 10 ohm are connected in parallel, and their equivalent resistance is R1. Three resistors with resistance values of 1 ohm, 10 ohm and 100 ohm are connected in parallel After (connecting), the equivalent is set to R2 A. R1 ＞ R2 B. R1 ＜ R2 C. R1 = R2 D. cannot be determined
• 16. In the series circuit of constant value resistor, sliding rheostat and ammeter, the voltmeter is connected in parallel at both ends of the resistor. If the voltage expression is 0 during the experiment, If the current indicator is 0 and the voltage indicator increases suddenly, what fault will happen?
• 17. In parallel circuit, if one resistance decreases, what is the current shared by this resistance and what is the voltage, resistance and power of the other resistance in parallel In a series circuit, if one resistance decreases, what is the current shared by this resistance, and what is the voltage, resistance and power of the other resistance in series
• 18. 1) 2) what is the function of resistance?
• 19. What is the maximum allowable voltage and current of a 2000 ohm resistor with a rated power of quarter watt?
• 20. A control circuit of hair dryer is designed. The sine input voltage of hair dryer is 50 Hz and 220 v. two resistors and position switches are required in the control circuit to realize three positions of 250 W, 500 W and 1000 W respectively. The equivalent circuit of switch in three positions of high, medium and low is drawn, and the component parameters are given