## anonymous 4 years ago Could I find the two missing angle measures if I know some of the side lengths of a right triangle?

1. anonymous

some means more than 1, right?

2. anonymous

Yeah, I'm pretty sure

3. anonymous

then with sine, cosine, tangent, you can find the angles

4. anonymous

yes, by using SAS congruents and those stuff. like.. a^2 = b^2 + c^2 -2ab Cos A

5. anonymous

im not really sure how to use them to find the angles instead of the other way around

6. anonymous

a^2 = b^2 + c^2 -2ab Cos A

7. anonymous

But if you know it's a right triangle, you don't use the cosine law

8. anonymous

Better only use a² + b² = c²

9. anonymous

Got it?

10. anonymous

that'll help me find the sides, but i need the angles

11. anonymous

sine theta = opposite/ hypotenuse cosine theta = adjacent / hypotenuse tangent theta = opposite/ adjacent

12. anonymous

Pythagorean theorem does not help to find angles

13. anonymous

Yeah

14. anonymous

so how do i use the trigonometric ratios to find the angles if i only know the right angle?

15. anonymous

im still confused xD

16. anonymous

then you use inverse sine/cosine/tangent

17. anonymous

okay, how do i use those? im a bit new at this

18. anonymous

The sum of the interior angles of a triangle are equal to 180 degree. To find the third angle of a triangle when the other two angles are known subtract the number of degrees in the other two angles from 180 degree :)

19. anonymous

i understand that, but i only know the 90 degree angle

20. anonymous

Let me show you the example so that you will get it better. :)

21. anonymous

@sweetrascal That has nothing to do with this

22. anonymous

Example: How many degrees are in the third angle of a triangle whose other two angles are 40degree and 65degree ? Answer: 180degree - 40degree -65degree = 75degree

23. anonymous

i only know the 90 degree angle... that's not what im looking for

24. anonymous

$\sin \theta = \frac{1}{2}$$\sin^{-1}\sin \theta = \sin^{-1} \frac{1}{2} \implies \theta = \sin^{-1} \frac{1}{2}$

25. anonymous

26. anonymous

hmm

27. anonymous

so both sides are multiplied by the inverse sine?

28. anonymous

not multiplied on your calculator there is a inverse sine buton

29. anonymous

okay, i get it! thank you!