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# without using a calculator write down the values of sin(-90), tan(-180) watch

1. how can i work it???? i know how to calculate using a graph but idk the other method the quadrant i could express using the quadrant
2. (Original post by hujikolp)
how can i work it???? i know how to calculate using a graph but idk the other method the quadrant i could express using the quadrant
You need to know how the sin, cos and tan graphs look like. They're periodic so if you know the basic shape, maxima/minima and intercepts from 0 - 360, you can work out these basic values for any value of x.
3. sin(-x)= -sin(x). Same goes for tan.
4. (Original post by Plagioclase)
You need to know how the sin, cos and tan graphs look like. They're periodic so if you know the basic shape, maxima/minima and intercepts from 0 - 360, you can work out these basic values for any value of x.
yes i do know
5. Use the fact that:

sin(-x)=-sin(x)
cos(-x)=cos(x)
tan(-x) = sin(-x)/cos(-x) = -sin(x)/cos(x) = -tan(x).
sin(-x)= -sin(x). Same goes for tan.
7. Tan and sin are odd functions so f(-x) = -f(x), then for sin you can use any of the 2 triangles (90,45,45 or 90,30,60) then just remember to add your minus back in

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Updated: February 23, 2018
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