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trig help as maths watch

1. how would you do the following: given that x is acute find cosx if sinx=0.5 . so I'm confused by the part thay says given it's acute? What effect does this have on the answer. by drawing the triangle I got root 3 over 2.
2. Acute means the size of the angle is between 0 and 90 degrees or 0 and pi/2 radians
3. Just means that only acute angles are valid whereas in other trig questions you would need to find other rots eg by adding 2pi for Cos angles. so in this case your answer of root 3 over 2 is the only answer as its acute
4. Can you provide a picture of the question? I remember answering a question very similar to this recently
5. (Original post by sigh1)
Just means that only acute angles are valid whereas in other trig questions you would need to find other rots eg by adding 2pi for Cos angles. so in this case your answer of root 3 over 2 is the only answer as its acute
thanks so what if it were obtuse etc. could there be two solutions and you'd have to plot the graph or something?
6. (Original post by jonjoshelvey21)
how would you do the following: given that x is acute find cosx if sinx=0.5 . so I'm confused by the part thay says given it's acute? What effect does this have on the answer. by drawing the triangle I got root 3 over 2.
You can use triangles to work this out as usual.

If was obtuse, then first of all, note that and in this region is negative and is positive. So, you can still use the triangle to work out the value of BUT you would need to change the sign of it to -ve
7. (Original post by jonjoshelvey21)
thanks so what if it were obtuse etc. could there be two solutions and you'd have to plot the graph or something?
If the angle was obtuse then its cosine would be negative.
8. (Original post by jonjoshelvey21)
thanks so what if it were obtuse etc. could there be two solutions and you'd have to plot the graph or something?
Sorry, I think I misunderstood the question when I first read this, I belive the acute part simply refers to the ASTC graph (a diagram showing where each trig function is positive) according to this graph, all the trig functions are positive in the first quadrant, ie 0-90deg or 0-pi/2.

So its just saying that when you find x by doing arc sine (how I would do it) dont muck about trying to get equivalent values by doing pi-x etc which you might normally do to find all values of x.
if sinx=0.5
then x=arcsin0.5=pi/6
cosx=cos(pi/6)=root3 over 2

Sorry if I confused you!

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Updated: February 10, 2018
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