Remember that the basic trig functions (sine, cosine, tangent) are just ratios of sides of right triangles. If you have a triangle with an angle of 34 degrees, then the ratio of the opposite side ...

We obtain the value of cos 25° by using the cos button on the calculator, followed by 25. This gives us: hypotenuse = 5.516889595 cm. So the length of YZ is 5.52 cm (to two decimal places).