Helpp ill mark u as brainlist

What basic trigonometric identity would you use to verify that sin x cos x tan x =1-cos^(2)x?

At the many chips cookie company they are serious about the number of chocolate chips in their cookies they claim that each cookie hasn't c chips. if their claim is true there will be 200 chips in 10 cookies

The midpoints of the sides of the large square are joined to form a smaller square. what is the area of the smaller square