a. +3.00 / -1.00 X 180 to the base curve + 6 D b. -2.00 / +1.50 X 90 to the base curve - 6D

b. -2.00 / +1.50 X 90 to the base curve - 6D

Answer to b +5.50DS / -6DS X 90/ -7.50DS X 180 Step one: -2.00 /+1.50 X 90 = -0.50 / -1.50 X 180 Step two Required spherical surface is -0.50 - (-6) = +5.50 DS Step three: -6.00 DS X 90 Step four: -6.00 + (-1.50) = -7.50DS X 180 The final toric formula is +5.50DS / -6DS X 90 / -7.50DS X 180