Posted by MAKITA on Friday, April 10, 2009 at 11:57pm.
1.)Find the exact solution algebriacally, if possible:
(PLEASE SHOW ALL STEPS)
sin 2x  sin x = 0
2.) GIVEN: sin u = 3/5, 0 < u < ï/2
Find the exact values of: sin 2u, cos 2u and tan 2u
using the doubleangle formulas.
3.)Use the halfangle formulas to determine the exact values of sine, cosine, and tangent of the angle: 15° .
4.) Use the sumtoproduct formulas to find the exact value of the expression:
sin 195°+ sin 105°
5.) Verify the identity algebraically:
(cos 4x  cos 2x)/2 sin 3x = sin x
THANKS IN ADVANCE!

MATH  MAKITA, Saturday, April 11, 2009 at 12:01am
CORRECTION FOR NUMBER 2! THE PI SYMBOL DIDN'T SHOW UP.
GIVEN: sin u = 3/5, 0 < u < pi/2
AND BTW, THAT "PLEASE SHOW ALL STEPS" IS FOR EACH PROBLEM. :)
THANKS.

MATH  Reiny, Saturday, April 11, 2009 at 12:10am
sin 2x  sin x = 0
I assume from the questions, that you are familiar with the common identities.
Also you don't state a domain, so I will asuume 0 ≤ x ≤ 2pi
2sinxcos  sinx = 0
sinx(2cosx  1) = 0
sinx = 0 or cosx = 1/2
from sinx = 0 , x = 0,pi,2pi
from cosx = 1/2, x must be in quadrants I or IV, so x = pi/3 or x = (2pipi/3) = 5pi/3
#2, you should recognize the 3,4,5 triangle and since u is in the first quadrant, cos u = 4/5 and tanu = 3/4
Now use your double angle formulas to find sin 2u etc.
#3
Hint 15º = 45º  30º
so sin15
= sin(4530)
= sin45cos30  cos45sin30
= √2/2(√3/2)  √2/2(1/2) = (√6  √2)/4
always check these with a calculator
now do the cosine and the tangent in a similar way.

MATH  Reiny, Saturday, April 11, 2009 at 12:15am
#4 hint: 195+105 = 300
195  105 = 90 mmmmhhhh!
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