There are two questions, I can solve the first one but not the second one with the same method. find the exact value of cot pi/4 in surd form. cot pi/4 = 1/ tan (pi/4) = 1 / tan 45 ( in degrees) = 1 / 1 = 1 which is the right answer according to the book. However when I tried the next question - sec 5 * pi / 4, there are problems. sec 5 * pi / 4 = 1 / cos (5 * pi / 4) = 1 / cos (900/4) ( in degrees) = 1/ cos(225) and then I am stuck here. How do I express this in surd form? The correct answer is minus(2^0.5) and all I know is cos45 = 1/root2, cos30 = root3/2 and cos 60 = 0.5 Can someone help me get to the correct answer?