Does reducing screen brightness increase battery life in laptop computers? To find out, researchers obtained 30 new laptops of the same brand. They chose 15 of the computers at random and adjusted their screens to the brightest setting. The other 15 laptop screens were left at the default setting - moderate brightness. Researchers then measured how long each machine's battery lasted. Was this an observational study or just an experiment? Justify your answer.

No , theres not enough information provided to Prove that both the triangles are congruent. Here in the figure we can see that there are two triangles ∆ BDA and ∆ BDC. And its given that

The congruence conditions for two ∆s are :-

1) SAS ( Side Angle Side )

→ Two triangles are said to be congruent by SAS if two respective sides of the two triangles and the included angle between two sides are equal.

2) AAS ( Angle Angle Side )

→ Two triangles are said to be congruent by AAS if two angles and one side of triangle is congruent to other two angles and one side of the triangle .

3) SSS ( Side Side Side )

→ Two triangles are said to be congruent by SAS if all the three sides of one triangle is equal to three sides of the other triangle.

4) RHS ( Right Hypotenuse Side )

→ In two right-angled triangles, if the length of the hypotenuse and one side of one triangle, is equal to the length of the hypotenuse and corresponding side of the other triangle, then the two triangles are congruent.

And the given data doesn't satisfies any of the conditions.