Which one of these is a square number?

15
39
81
132

What is the point of inflection for the function f(x)=2cos4x on the interval (0, pi/2)

My final challenge question of the day! i have no tests, nothing to do this for, it is simply giving away free points for a you tube video! so 50 free points for answering the most simple question ever! here is the key to getting brainiest for this question. answer in under 50 seconds. you think you can do it. i think you can. here is the question: 1x2= i know! easiest question ever! and yes! if you answer this question, you will be on you so come on and get the free 50 while you can!

Given: lkm jkm, clmk prove: alkmajkm jmk. choose the word that completes the sentence correctly. proof: lkm jkm and lmk * umk are given. km km by the property of congruence. equivalence symmetric reflexive transitive