Trig: simplifying, evaluating, rewriting, solving (5 probs)

[ShanikaC]

Simplify

sec x cos(pie/2-x)

Evaluate
sin105

Simplify
sin8x cos2x+ cos8x sin2x

Rewrite ae a sum
sin7x sin3x

find all solutions in the interval[0,2pie)
8sin(x/2)-8=0

 

[happy]

Re: Trig

Simplify



Evaluate
sin105

Oh, you couldn't do that one on your calculator? FYI- Pie is something you eat. Do you mean pi? Also, I believe in the rules it says to not post a list of problems and to show all your work.

 

[skeeter]

Re: Trig

Simplify

sec x cos(pie/2-x)
hint: cos(pi/2 - x) = sinx

Evaluate
sin105
hint: sin(105) = sin(60 + 45) ... also, see next hint

Simplify
sin8x cos2x+ cos8x sin2x
sin(a+b) = sin(a)cos(b) + cos(a)sin(b)

Rewrite ae a sum
sin7x sin3x
only thought I can come up with is the identity
sin(a)sin(b) = (1/2)cos(a-b) - (1/2)cos(a+b)

find all solutions in the interval[0,2pie)
8sin(x/2)-8=0
sin(x/2) has to be equal to 1, correct? where is that?