47.7k views
3 votes
Find the exact value of the expression. Write the answer as a single fraction. Do not use a calculator.


sin (3 \pi )/(2) tan ((-23 \pi )/(4)) - cos ((-10 \pi )/(3))
Simplify your answer. Type an exact answer, using radicals as needed. Use integers or fractions for any numbers in the expression. Rationalize all denominators.

1 Answer

3 votes

Use:\\sin(x+y)=sinxcosy+sinycosx\\\\tan(-x)=-tanx\\tan(k\pi+x)=tanx\\\\cos(-x)=cosx\\cos(2k\pi+x)=cosx\\cos(x+y)=cosxcosy-sinxsiny



sin(3\pi)/(2)=sin(\pi+(\pi)/(2))=sin\pi cos(\pi)/(2)+sin(\pi)/(2) cos\pi=0\cdot0+1\cdot(-1)=-1\\\\tan\left(-(23\pi)/(4)\right)=-tan(23\pi)/(4)=-tan\left[6\pi+\left(-(1)/(4)\pi\right)\right]=-tan\left(-(1)/(4)\pi\right)=tan(\pi)/(4)=1


cos\left(-(10\pi)/(3)\right)=cos(10\pi)/(3)=cos\left(2\pi+1(1)/(3)\pi\right)=cos\left(1(1)/(3)\pi\right)=cos\left(\pi+(\pi)/(3)\right)\\=cos\pi cos(\pi)/(3)-sin\pi sin(\pi)/(3)=-1\cdot(1)/(2)-0\cdot(\sqrt3)/(2)=-(1)/(2)\\\\sin(3\pi)/(2)tan\left(-(23\pi)/(4)\right)-cos\left(-(10\pi)/(3)\right)=-1\cdot1-\left(-(1)/(2)\right)=-1+(1)/(2)=-(1)/(2)
User Foti Dim
by
8.4k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories