# Right triangle in trig

• May 27th 2010, 09:40 PM
Right triangle in trig
Hi, I am having trouble with this problem. My Geometry text book explains how to do this, but not very well, and I have come to a problem on a practice test that is nothing like what's in the book. I would really appriciate some help with this please!

*Figure is a right triangle

Question: Given the Figure below (right triangle), find ,
a if sin B = 0.42, cos B = 0.91, tan B = 0.47 and c =60

Thank you very very much! :)
• May 28th 2010, 12:38 AM
kompik
Quote:

Originally Posted by Polkadotprincess19
Hi, I am having trouble with this problem. My Geometry text book explains how to do this, but not very well, and I have come to a problem on a practice test that is nothing like what's in the book. I would really appreciate some help with this please!

*Figure is a right triangle

Question: Given the Figure below (right triangle), find ,
a if sin B = 0.42, cos B = 0.91, tan B = 0.47 and c =60

Thank you very very much! :)

Since you know the value of sin B and c, you could simply use the equation
sin B=b/c
to calculate b and then plug this into Pythagorean theorem
a^2+b^2=c^2
to get a.

But even simpler: If you know that in right triangle sin A=cos B, then you have
cos B=sin A=a/c
from which you can easily get a.

(I guess that A is the angle opposite to the side a and B is the angle opposite to the side b - this is probably shown in the figure you did not show us. Am I right?)
• May 28th 2010, 12:39 AM
earboth
Quote:

Originally Posted by Polkadotprincess19
Hi, I am having trouble with this problem. My Geometry text book explains how to do this, but not very well, and I have come to a problem on a practice test that is nothing like what's in the book. I would really appriciate some help with this please!

*Figure is a right triangle

Question: Given the Figure below (right triangle), find ,
a if sin B = 0.42, cos B = 0.91, tan B = 0.47 and c =60

Thank you very very much! :)

1. Use the definition of the trigonometric functions in a right triangle:

$\sin(B)=\frac bc$

$\cos(B)=\frac ac$

$\tan(B)=\frac ba$

2. Choose the appropriate equation to calculate a.
• May 28th 2010, 04:24 PM