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I'm really bad at this and don't even know the names of the different things, so here it is as plain as I can ask. I have a trigonometry calculator & need to know how I should enter the formula to get my answer.

I have a triangle. One angle is 90 degrees and the other is 5 degrees. I don't know the 3rd angle & it doesn't matter to me. I know 1 side is 78 inches. the other long side (near 78") doesn't matter, but I need to know the measurement of the short side across from the 5 degree angle.

I need the formula to enter so I can get the short side of the triangle when putting in various different measurements other than the 78.

Sorry I don't know how to draw here. Just know that the triangle I'm looking at has one side running the length of the bottom (left to right). The 5 degree angle is the one on the bottom left and the 90 degree angle is on the bottom right. The 78" side I'm talking about is the side on top slanting from bottom left to top right. The straight, short side running from the bottom right (the 90 degree angle) to top right (where the slanted side connects to it.

BlueJade
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First off, the third angle is $180^o - (90^o + 5^o) = 85^o$

As to the question at hand, if you have a right angle triangle, you can use some basic trigonometric identities to come to an answer. Most notably,

$$sin \theta = (length\ of\ the\ opposite \ side) / (length\ of\ the\ hypotenuse)$$

Unfortunately, without a more complete description of the triangle, or which calculator you are using, I can't help you more than this. This, however, should be enough to get you going on finding the answer yourself.

peggylux
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  • I don't understand that, And, I'm not sure what else I need to describe for a complete description of the triangle. What would the length of of the short side be with that 5/90/85 degree triangle? (Given that 1 of the longer sides is 78)? – BlueJade Oct 18 '17 at 22:48
  • @BlueJade What part do you not understand? – peggylux Oct 18 '17 at 22:49
  • The relationship between where the angles lie on the triangle and where the side of length 78 lies on the triangle. For instance: it may be the length of the hypotenuse (the side opposite the angle of 90°) or it may not be. – peggylux Oct 18 '17 at 22:53
  • OK. If the hypontenuse is the side across from the 90 degree angle, then that's the side I know is 78". So how do I find the length of the short side? (the side going straight up & down between the 90 degree angle & the right side of the hypotenuse side)? – BlueJade Oct 19 '17 at 07:08
  • I'm not getting the answer to my question. Can anyone else weigh in? – BlueJade Oct 23 '17 at 22:54