It looks like you've uploaded a document with some mathematical exercises involving trigonometry, focusing on calculating angles and lengths in right triangles.

Here’s a quick overview of the tasks:

Exercice 1:

• Triangle ABC is a right triangle at A with sides AB = 4 cm and BC = 7 cm. a. You need to calculate the measure of the angle ∠ABC (denoted as $\hat{ABC}$) rounded to the nearest degree. b. Based on that, you'll then deduce the measure of the angle ∠ACB.

Exercice 2:

• Triangle RST is a right triangle at R, with RT = 4.3 cm and $\hat{RTS} = 55^\circ$. a. You are asked to calculate the length of side ST, rounded to one decimal place.

Exercice 3:

• This exercise involves multiple steps.
  1. Calculate the distance BC.
  2. Calculate the approximate angle ∠BA (rounded to the nearest degree).
  3. Calculate the length of side DC, rounded to one decimal place.

Exercice 4:

• A few more calculations for a right triangle.
  1. Calculate the measure of ∠ACB.
  2. Calculate the length of side AC, rounded to the nearest tenth.
  3. Calculate the length of side BC, rounded to the nearest tenth.

Would you like me to work through one of these exercises in detail, or would you prefer an overview of how to approach solving them?