Given: ABCD rectangle AB = 8cm, BC = 15cm AC-diagonal Find: sin and cos of angle BAC, AC? Decision: ?

The AC diagonal divides the rectangle into two right-angled triangles: ABC and ADB.

Consider a triangle ABC.
Leg AB = 8 cm, leg BC = 15 cm.
Let us calculate the length of the hypotenuse AC by the Pythagorean theorem:
AC² = AB² + BC² = 8² + 15² = 64 + 225 = 289
AC = √289 = 17 cm.

Find the sine and cosine of the angle BAC using their definition:
sin BAC = BC / AC = 15/17 = 0.88235;
cos BAC = AB / AC = 8/17 = 0.47059.