HELP
The measure of side BC =

D

Step-by-step explanation:

Using the cosine ratio and the exact value

cos45° = , then

cos45° = = = = ( cross- multiply )

2BC = n ( divide both sides by 2 )

BC = → D

5

step-by-step explanation:

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.