this key sequence implements the triangle formula c = sqrt(a^2+b^2-2*a*b*cos theta) to find the length of the side opposite sides a & b including angle theta.
x<>m 1 * HLT x<>m 2 * HLT F cos * 2 +/- = x<>m 3 mr 2 * = m+ 3 mr 1 * = + mr 3 = sqrt HLT
to execute, enter a, press S to start, enter b, press S again, enter theta and press S again. the display halts with the length c. be sure to switch to degrees if necessary. it appears that S continues the program, pressing C to clear automatically resets the program counter to the beginning.