(x cosa + y sina)^2 + (x sina - y cosa)^2 = x^2+ y^2 proove this

This is some trig saying that when we rotate the point around the origin by any angle the point we end up with is the same distance from the origin as the original point.

That doesn't matter. There's nothing tricky about this one, we just have to multiply it out and see where we are.

Collect terms, and let the cross products (with the 2) cancel.

because of course

plz mark brainliest i took the test

46

step-by-step explanation:

given

height = 168 cm

formula

height =2.47*f+54.13

solution

168 = 2.47f + 54.13             subtract 54.13 from both sides

168 - 54.13   = 2.47f             combine

113.87 = 2.47f                     divide by 2.47

113.87 / 2.47 = f                   combine

46.1 = f  

answer: 46 cm