use doublr or half angle formulas..
1. cos 105 deg
2. cos 165 deg
pls show your solutions..tnx..
2006-08-21 01:51:33 · 5 answers · asked by leo 2 in Science & Mathematics ➔ Mathematics
cos105=cos(60+45)=cos60.cos45-sin60.sin45
cos165=cos(180-15)=cos180.cos15-sin180.sin15
cos(2A)=2cos^2(A)-1=1-2sin^2(A)[formulae]
put A=15 &calculate values of cos15 & sin15. THEN U WILL GET THE VALUES OF cos105 &cos165
hope u got ur answer. :-)
2006-08-21 06:51:28 · answer #1 · answered by priya 2 · 0⤊ 0⤋
the cos ,sin tan of 30 , 45, 60, 90 you should know.
105 = 60 + 45
2006-08-21 09:37:18 · answer #2 · answered by gjmb1960 7 · 0⤊ 0⤋
The answer is cos 105= -0.258819045.
cos 165=-0.965925826.
I cant show you calculations because they are too big.
2006-08-21 09:22:30 · answer #3 · answered by Anonymous · 0⤊ 0⤋
Well you need cos tables or a calculater for that. I have mine close at hand so I'll look. Ok, cos 105deg = -0.2588, and cos 165deg = -0.9659.
2006-08-21 08:58:17 · answer #4 · answered by Put_ya_mitts_up 4 · 0⤊ 0⤋
cos105=cos(60+45)
cos165=cos(120+45)
Now solve this
2006-08-21 09:50:46 · answer #5 · answered by RIMA 3 · 0⤊ 0⤋