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Note: The area of the triangle ABC can be used as the bottom and CF as the height.

It can also be calculated by using AC as the bottom and be as the high.

So ab*cf 2=ac*be 2

Because ab=ac

So cf=be

Because be ac at point e, cf ab at point f

s△abc=1/2ab*cf=1/2ac*be

Because ab=ac, be=cf

Since be ac, be is the height of ac, cf ab so cf is the height of ab, the triangle area s=ab*cf 2=ac*bf 2, it is known that ab=ac, so be=cf.

Hope it helps!

This problem can be solved by proving that BEC and CFB are congruent.

Since AB = AC, BCE= CBF, and BEC= CFB=90°, BC=CB, then BEC CFB(AAS).

So be=cf

According to the prompt, we can solve 1 2*ab*cf=1 2*ac*be because ab=ac, so be=cf

The area of the triangle = cf * ab = be * ac because ab = ac so be = cf

Solution: Let the uphill speed be v1 and the flat road speed be v2

20/v1+20/v2=50/60

10/v2+30/v1=45/60

Solution: v1 = 60 km s v2 = 40 km s

Uphill speed v1, flat road speed v2 units km s

20/v2+20/v1=50*60

10/v1+20/v2=45*60

The speed of the car on the uphill and flat road is x,y

20/x+20/y=50

10/y+30/x=45

x=1(km/min ) y=2/3(km/min)

(1) Let v=a*t+b

When t=0, v=25 is 25=a*0+b---b=25 When t=2, v=5 is 5=a*2+b, and from b=25, a=-10 is v=-10t+25

2) When the highest point is reached, v=0, that is, -10t+25=0 to get t=seconds).

1) Let the function be v=at+b

From the question 25=a*0+b 5=a*2+b, we get a=-10 b=25

then v=-10t+25

2) When v=0, t=seconds.

When it comes to physical knowledge, v on = v at the beginning -gt

25-10x2=5 (10 for g is fine.)

So the first question v=25-10t

The second question is that the highest point velocity is 0

So 0=25-10tt=

1. Let the analytic formula be v tk b and get v 25, t and t 2 respectively.

25 b,5 2k b find k 10 and the analytic formula set by k 10,b 25 generations gives v 10t 25

2. Take the analytic formula v 10t 25 that the v 0 generation asks for to get t seconds.

The highest point is reached after seconds.

90 process: pass point A to do the BC vertical line at point H point, through point C to do AD vertical line at point I, and then you can calculate it.

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1.Solution: Let A and B hit x and y respectively every hour; Then 6x = y=12 15x, x=15 12y

The total number of manuscripts is 4(x+y)+6y, divided by the respective speeds:

A requires: [4(x+y)+6y] x=12 hours.

B requires: [4(x+y)+6y] y=15 hours.

A: It takes 12 hours for A to complete this manuscript alone, and 15 hours for B to complete this manuscript alone.

It takes X hours for A and y hours for B. then there is (4(1 x + 1 y) + (6 x) = 1, 6 x = . The solution yields x=12 and y=15