minta tolong dong gimana cara penyelesaian nya

[tex]KM= \sqrt{8^{2} + 15^{2}} \\ KM= \sqrt{64+225} \\ KM= \sqrt{289} \\ KM=17...(1) \\ \\ KN= \sqrt{17^{2}-7^{2}} \\ KN= \sqrt{289-49} \\ KN= \sqrt{240} = 4 \sqrt{15}...(2) \\ \\ cos (x+y)=cos(x)cos(y) - sin(x)sin(y) \\ cos(x+y)= \frac{15}{17} [tex]KM= \sqrt{8^{2} + 15^{2}} \\ KM= \sqrt{64+225} \\ KM= \sqrt{289} \\ KM=17...(1) \\ \\ KN= \sqrt{17^{2}-7^{2}} \\ KN= \sqrt{289-49} \\ KN= \sqrt{240} = 4 \sqrt{15}...(2) \\ \\ cos (x+y)=cos(x)cos(y) - sin(x)sin(y) \\ cos(x+y)= \frac{15}{17} . \frac{4 \sqrt{15} }{17}- \frac{8}{17} . \frac{7}{17} \\ cos (x+y) = \frac{60 \sqrt{15}}{289}- \frac{56}{289} \\ cos(x+y)= \frac{60 \sqrt{15}- 56}{289} [/tex]