Homework Help: precal

Posted by bee on Monday, December 3, 2012 at 10:02pm.

when solving for all solutions how do I work out this problem: cos4(alpha)=cos2(alpha)
and when verifying each identity how do I complete this problem: sin (alpha/2)=sec alpha -1/2sin (alpha/2)sec alpha

precal - Steve, Monday, December 3, 2012 at 11:53pm
cos4x = cos2x
2cos^2(2x)-1 = cos2x
2cos^2(2x)-cos(2x)-1 = 1
(2cos2x+1)(cos2x-1) = 0
so, cos2x = -1/2 or 1
cos 2pi/3 = cos 4pi/3 = -1/2
cos 0 = 1

as for the identity, I get the feeling there's a typo, because secx appears twice on the right.

Answer this Question

Related Questions

Trigonometry - Find the counterexample to shows that the equation sec (alpha) - ...
trig - FInd the exact value pf the 6 trig function of alpha Given: point (-2,-6...
trig - express 20sin theta + 4 cos theta as R sin(theta + alpha) R sin(theta + ...
maths - if alpha and beta are the zeros of the polynomial 2x^2-4x+5 then find ...
trigonometry - given that sin alpha/2 = 2/3, and that alpha/2 is in quadrant II...
Trig - assume A= alpha using complementary rule how do I solve for alpha? cos(2A...
trig - Please find sin (alpha/2) and cos (alpha/2) sec alpha = 3, -pi/2 &lt...
business law - Alpha Corporation in Boston offers a job to Carol, who lives in ...
another college math question - Please teach me. I am completely blank with it...
Trigonometry - Write cos(-83degrees) as a function of a positive angle Prove ...

For Further Reading

First Name:
School Subject:
Answer: