English Deutsch Français Italiano Español Português 繁體中文 Bahasa Indonesia Tiếng Việt ภาษาไทย
All categories

2006-08-28 06:04:09 · 13 answers · asked by iluvhipos 3 in Science & Mathematics Mathematics

13 answers

The cosine of an angle is defined as the sine of the complementary angle. The complementary angle equals the given angle subtracted from a right angle, 90°. For instance, if the angle is 30°, then its complement is 60°. Generally, for any angle t,

cos t = sin (90° – t).
Written in terms of radian measurement, this identity becomes

cos t = sin (∏/2 – t).

Right triangles and cosines
Consider a right triangle ABC with a right angle at C.

please click on this link before u read below; thanks

http://www.largeimagehost.com/image/upload-image/free-image-host/1880/Strig30.JPG.html

A = 30°, (90° - A) = 60°


Consider the triangle PQR (drawing) with all three angles equal to 60°. By symmetry, all three sides are equal too (a more rigorous proof exists, but we skip it). Drop a line QS perpendicular to PR: it divides the big angle into two right-angled triangles with sharp angles of (30°, 60°), which is the kind we are interested in. By symmetry, the triangles are of equal size and shape ("congruent") and therefore (skipping another proof)

SR = (1/2) PR
In the notation of the drawing


a = (1/2) c

a/c = 1/2 = sin 30° = cos 60°
Continuing
sin2 30° = 1/4
But
sin2 30° + cos2 30° = 1
So
1/ 4 + cos2 30° = 1
Subtract 1/4 from both sides

cos2 30° = 3/4

cos 30° = SQRT(3)/ SQRT(4) = SQRT(3)/2 = 1.7320508/2

cos 30° = 0.8660254 = sin 60°

so you see they are equal.

Good question and Good luck

2006-08-28 12:11:26 · answer #1 · answered by sweetie 5 · 5 0

If the 30 and 60 are in degrees, then they are equal. If they are in radians (which is the default), then sin 60 is larger.

2006-08-28 06:56:20 · answer #2 · answered by mathematician 7 · 3 0

They are equal.

sin(a) = cos(90 - a), so if a = 30 deg

sin(60) = cos(90 - 60), sin(60) = cos(30)

perhaps you must know that

sin(60) = cos(30) = sqrt(3)/2

2006-08-28 06:44:34 · answer #3 · answered by Dimos F 4 · 1 1

Equal.

2006-08-28 09:34:47 · answer #4 · answered by Sk8erboi83 3 · 0 0

Equal.

2006-08-28 06:08:22 · answer #5 · answered by Kerk 2 · 1 0

both values are equal
sin60 = cos [90-@]
@=theta

therefore
sin60=cos[90-60]
sin60=cos30
hence proved

2006-08-28 06:09:04 · answer #6 · answered by nave 1 · 2 0

BOTH ARE EQUAL.
sin 60 =0.866
cos 30=0.866

2006-08-28 06:09:30 · answer #7 · answered by Anonymous · 1 0

in case you do degrees, they're both .886, and in case you do radians, this is sin60 = -.305 cos30= .154 in case you do not understand or you probably did not study radians in college, then purely flow with degrees and say they're both .886

2016-12-05 19:39:51 · answer #8 · answered by barras 3 · 0 0

Both are the same No questions about that!!

2006-08-28 06:18:54 · answer #9 · answered by CodeRed 3 · 1 0

Hey!
they are equal if they are in degrees

2006-08-31 08:40:55 · answer #10 · answered by Marla 3 · 0 0

fedest.com, questions and answers