Cho mình hỏi sao từ dòng ĐK suy ra -cos2x được ạ ?

Which math sentence can be used to determine if the triangle is a right triangle?

Write an introductory paragraph for this corrie ten boom and her family were faced with some difficult choices after hitler came to power. some family members paid the ultimate price. write a carefully thought-out paper of at least 200 words dealing with the following concepts: --how should a christian act when evil is in power? --what do you think it would be like to live in an occupied country? remember to proofread anything you write thoroughly.

If the scale factor between two circles is 2x/5y what is the ratio of their areas?