Question

If one angle of a parallelogram is a right angle prove that it is a rectangle

Answer 1

opposite angles in a //gm are equal (given)
therefore if one is 90° it's opposite will also be 90°
similarly,
the sum of the remaining angles will be 180 and each angle will be 90° as each angle is equal and hence given //gm is a rectangle as each angle is 90°

Answer 2

its simple,
if one anngle of a parallelogram is 90 degree.....
then u just hav to prove one pair of opposite sides 90 degree.. hence two opposite angles are 90 degree.. by linear pair u can also prove other two angles 90 degree and it will form a rectangle..
hope u understood what i said.. i jus gav u explaination so that u would remember these points when u r doing this question coz if i'll giv u answer u would jus copy nd write...so that's why i gav u explaination