I need help trying to determine what number is suppose to be in place foralpha? I do not understand how they came up with Cos = 1/4 in question (d).

Sin(90 deg - alpha) = Cos alpha = 1/4

http://i333.photobucket.com/albums/m...g?t=1221333118

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- September 13th 2008, 11:18 AMrobascTrigonometric Identities
I need help trying to determine what number is suppose to be in place for

**alpha**? I do not understand how they came up with Cos = 1/4 in question (d).

Sin(90 deg - alpha) = Cos alpha = 1/4

http://i333.photobucket.com/albums/m...g?t=1221333118 - September 13th 2008, 11:32 AMMoo
Hello,

can be checked on a unit circle.

Otherwise, use this formula :

So here

The red parts are supposed to be known (Wink)