# Drawing a parallelogram (given a, the sum of the 2 diagonals and the angle between a and a diagonal)

1. Oct 5, 2014

### Redinorun

I'd really need help with this. Thanks.

1. The problem statement, all variables and given/known data

Draw a parallelogram:
a = 4cm
e + f (diagonals) = 11cm
angle between a and e = 22°

2. Relevant equations
2 and 2 sides are parallel
both diagonals halve each other
(diagonal e goes from A to C)

3. The attempt at a solution
(attachment)

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2. Oct 5, 2014

### ehild

Go ahead with your attempt! You have drawn the blue triangle. PRS is isosceles. Halve the side RS and draw a perpendicular at the halfpoint. It defines point P.

ehild

3. Oct 5, 2014

### Redinorun

Thanks, got it. You're a life saver. By the way: Why wouldn't this work if a = 8cm? Is it because a would be longer than the sum of e and b (if we take half of it as a triangle)? Or is there another explanation?

4. Oct 5, 2014

### ehild

a can not be longer than (e+f)/2. The yellow triangle would not exist.

5. Oct 5, 2014

### Redinorun

Thank you! (I menth something like that, yes)