Posted by Jon on Sunday, November 4, 2012 at 8:08pm.
9pi/12 should be converted into degrees. The value of pi is 180 so all you do is 180 times 9 divided by 12 and then take the cosine of that value.
cosx cosy + sinx siny = cos(x-y)
so, what we have here is
cos(9π/12 - 5π/12) = cos(4π/12) = cos π/3 = 1/2
Related Questions
math - Eliminate the parameter (What does that mean?) and write a rectangular ...
calculus - pleaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaasw help can you ...
math - Use the exact values of the sin, cos and tan of pi/3 and pi/6, and the ...
Public High School Pre Calculus HH - Ok I do not know how to do this problem. I ...
Pre-Cal - Find the 5 roots of x^5+1=0 in polar and Cartesian form. (x^5 means x ...
Math(Please help) - 1)tan Q = -3/4 Find cosQ -3^2 + 4^2 = x^2 9+16 = sqrt 25 = 5...
Math - Find the quotient 3(cos (5pi/12) + i sin (5pi/12) / 6(cos (pi/12) i sin (...
Math(Please help) - 2) Use the sum and difference identites sin[x + pi/4] + sin[...
Pre Calculus - ok I appologize for my stupidity... I'll answer your question...
trig - Give exact answers Sin(11pi/8) so this is sin(pi/4+pi/3) sin(pi/4)*cos(pi...
For Further Reading
