Posted by Matt on Tuesday, May 19, 2009 at 8:06pm.
where is the sine negative?
Isn't it in quadrants III and IV ?
The sine of which angle is 1/2 ?
Isn't it 30º or pi/6 radians
so arcsin (-1/2) is 210º or 330º
which would be 7pi/6 or 11pi/6 radians
Sorry, my mistake. It is arccos, not arcsin. Also, the negative in the book is exactly in the middle. The book just says evaluate the expression.
first of all
-1/2 = 1/-2 = -(1/2)
it makes no difference where the negative sign is
just repeat my steps from above, except use the properties of Cosine
1. the cosine is negative in the 2nd and 3rd quadrants.
2. cos (60 degrees) = cos pi/3 = 1/2
(hint: one of the answers is 2pi/3)
But how do I know where cosine (or tangent and sine) are positive? I don't understand.
Thanks for the help, btw.
It is called the CAST rule
this page explains it well
http://www.worsleyschool.net/science/files/cast/castdiagram.html
It all makes sense now!!!! Thanks, haha.
Related Questions
Precal - Use a calculator to evaluate the expression. arcsin 0.45 arctan 15 ...
Pre-Calc help NOW PLEASE!!! - Evaluate the expression under the given conditions...
Pre-Calc - Write an algebraic expression that is equivalent to the expression (...
trig - I do not understand for my life how to solve this problem. Evaluate the ...
Pre-Calculus - Evaluate the expression under the given conditions.? show work ...
Pre-Calc Help - Evaluate the expression under the given conditions. (show work ...
Pre-Calc Help!!!!!!!! - Evaluate the expression under the given conditions. sin...
Trigonometry - Usa a right triangle to write each expression as an algebraic ...
Trigonometry - Write the trigonometric expression as an algebraic expression. 1...
math 115 - 1. divide 36/-4= 9 is this correct? 2. evaluate the expression |-5 +3...
For Further Reading
