Finding side a, given side b and the angles.

nathanralph

New member
Joined
Aug 27, 2005
Messages
27
Well this should be pretty simple. Below is the question, as well as how I worked it out. Seems like this should be right, the the question states to use a square root notation in the answer. Am I doing something wrong here? How would I come up with a square root?

help.jpg
 
If you use the exact value, you solve it as requested.

tan(30º) = 1/sqr(3)

Some students need to turn off their calculators. You may not be one of them. Just a thought.

P.S. GREAT WORK on showing us the entire problem statement AND your workings. Very, very nice. May you infect other students with your thorough disclosure. :)
 
Yes, but, a few notes:

1) You can enter exercises textually:

. . . . .Given: Triangle ABC, with sides a, b, and c,
. . . . .with side a opposite the angle at point A, and
. . . . .so forth.
. . . . .Triangle ABC is right, with m(ACB) = 90°,
. . . . .m(BAC) = 30°, and m(ABC) = 60°.
. . . . .Also, the length of side b is 20 units.

. . . . .Find: the length of side a.

2) You can use what you learned back in trig and/or geometry:

. . . . .The three sides of a 30-60-90 triangle are,
. . . . .in order of length, in the ratio 1:sqrt(3):2.

. . . . .To get "20" for the "sqrt(3)" side, you'd have
. . . . .to multiply by 20/sqrt(3). Similar triangles
. . . . .have all their corresponding sides in
. . . . .proportion, so we can find the length of a,
. . . . .the shortest side, by multiplying by the same
. . . . .amount. Then:

. . . . .a = (1)(20/sqrt(3)) = 20/sqrt(3) = [20sqrt(3)]/3

This exact answer (which might be what the instructor is looking for, and his note about how to format square roots would imply that it is) evaluates to the same decimal you got.

3) You can post geometry problems to the "geometry" category.

Thank you for showing all of your work. (I reposted it as text partly to show you how it can be done, but mostly because image calls are notoriously twitchy -- I don't know why -- and later visitors might not be able to see what you're working on.)

Good work!

Eliz.
 
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