Total internal angle: (n-2) x 180-degree

n- number of sides the polygon has.

Since parallelogram has four sides.

Attachment:

parallelogram (2).jpg [ 45.77 KiB | Viewed 281 times ]
It has four sides.

2. Plugging it into the equation above, Sum of interior angle= (4–2) x 180

3. Sum of interior angle= 360°.

You may think of square and rectangle which have four sides, and yeah they have the same sum of the interior angle which is 360°.

Conclusion: any angle is 90°

Hope this helps.

Source

Quora
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