Find the length of side x. Give your answer to 1 decimal place.
105°
15 cm
18 cm
х

Explanation:

Let's make A = 105 the given angle. The side opposite this is 'a'

The two given sides are b = 18 and c = 15

Use the law of cosines to find side 'a'

a^2 = b^2 + c^2 - 2*b*c*cos(A)

x^2 = 18^2 + 15^2 - 2*18*15*cos(105)

x^2 = 324 + 225 - 540*cos(105)

x^2 = 324 + 225 - 540*(-0.258819045102521 )

x^2 = 324 + 225 + 139.762284355361

x^2 = 688.762284355361

x = sqrt(688.762284355361)

x = 26.2442809837755

x = 26.2

Side note: make sure your calculator is in degree mode.