Please help me, i need the answer please

What is sin 7x/4 ? i need on this urgent trig

Prove the converse of the pythagorean theorem using similar triangles. the converse of the pythagorean theorem states that when the sum of the squares of the lengths of the legs of the triangle equals the squares length of the hypotenuse, the triangle is a right triangle. be sure to create and name the appropriate geometric figures.

For the following equations, find the ratio of a to b. be sure to show all of your work. a. 3a = 6b b. 15a = 5b