- #1

- 308

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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?