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@mathmate could you help please?
Typically, when two sides of a triangle and the included angle is known, you can use the cosine rule to find the third side, and then sine rule to find the remaining angles.
Okay the cosine rule is a^2=b^2+c^2-2bc cosA So if I plug that in i get a^2=4^2+3^2-2(4)(3) cos(15 degrees) a^2 is approximately 1.8 sqrt 1.8 = aproximately 1.35 Is that right??
Yes, 1.348251 to be closer, but yes, 1.35 is correct!
However, you need more figures to do the sine rule calculations, or else you angles will be off!
For my first question. To find the angles would I set up ratios? If so, i got 1.8/ sin(15)= 4/ sin b Then i would cross multiply??
Exactly, but 1.348/sin(15)...
oh yeah. how about my second problem?
The same strategy for the second problem, since two sides and included angle are known. The fact that 108 > 90 degrees does not matter, because cos108 will then be negative, and everything will work out.
So use the cosine rule?
Yep, cosine rule, followed by sine rule (whenever 2 sides and included angle are known).
I get: a^2=13^2+11^2-2(13)(11) cos(106) but when i plug this in i get- 368.32 and the square root it and get: 19.205 is that right?
I get 19.4520 , you can double check my number. Sorry, gtg.
I still get 19.205 but thank you!
I think the angle is 108, unless I made a mistake. @haileycaroen
I think the angle is 108, unless I made a mistake. @HaileyJCaroen