# Trig - check my answers plz!

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1. (P -15/17, -8/17) is found on the unit circle. Find sinΘ and cosΘ

Work:
P= (-15/17, -8/17)
cosΘ = a value
P = (a,b)
sinΘ = b value

cosΘ = -15/17
sinΘ = -8/17

2. Should the triangle be solved beginning with Law of Sines or Law of Cosines. THen solve the triangle and found to the nearest tenth. a = 16, b = 13, c = 10.

Work:
c^2 = a^2 + b^2 -2abcosC
100-16^2+13^2-2*16*13cosC
100= 256+169 -416cosC
100=425-416cosC
-325=-416cosC
.78125=cosC

Answer: 38.6°, Law of Cosines is used

3. Should the triangle be solved beginning with Law of Sines or Law of Cosines. Then solve the triangle and round to the nearest tenth. A = 56 degrees, B = 38 degrees, a = 13.

Work:
SinA/a = SinB/b
sin56/13= sin38/b

3. Find the exact value of tan(-3pi)

Work: tan(-3pi) = tan(-3pi+2pi) = tan (-pi) = tan (-pi+2pi) = tan (pi) = sin(pi)/cos(pi) = (0)/(-1) = 0

• Trig - check my answers plz! -

correct.

• Trig - check my answers plz! -

simplify the expression tan 20 degrees +tan 25 degrees/ 1-tan 20 degrees tan 25 degrees