# Math

Cos180* - Sin90* + Cot45* - Csc30* - Sec240* - Tan315*

How do I do this?

1. 👍 0
2. 👎 0
3. 👁 40
1. all these are standard angles for which you should know the trig ratios

cos 180 = -1 , look at the cosine curve
sin 90 = 1 , look at the sine curve
cot 45 = 1/tan45 = 1/1 = 1 , look at your 45-45-90 triangle
csc 30 = 1/sin30 = 1/(1/2) = 2 , look at the 30-60-90 triangle
sec 240 = 1/cos240 = - 1/cos60
= -1/(1/2) = -2 , using the CAST rule and 30-60-90 triangle
tan 135 = -tan45 = -1

1. 👍 0
2. 👎 0
posted by Reiny
2. these are all standard angles you should know by heart. It will save you a lot of trouble working them out all the time.

-1 - 1 + 1 - 2 + 2 + 1 = 0

It also involves knowing the signs of the trig functions in the various quadrants, and how to figure the reference angle.

Also, lose the capitalization.

1. 👍 0
2. 👎 0
posted by Steve

## Similar Questions

1. ### f math

given that sin (90-5 t ta )=cos180 - t ta...find d value of t ta

asked by mercy on November 20, 2016
2. ### trig.

How is it that sin90 is negative?

asked by Gene on May 30, 2012
3. ### math trigonometry

Simplify cos180*sin225*cos80/sin170*tan135

asked by kem on June 10, 2015
4. ### Polar equations - Help?

i need to graph the polar equation 2 = r cos (theta + 180) on one of the graphs that looks like a flattened globe. So far I have 2=r cos180 costheta + r sin180 sintheta what do i do now?

asked by Tabby on April 20, 2012
5. ### maths

1/tan60';sin90',tan60';...form a sequence. Calculate the fourth term.

asked by jay on February 26, 2015
6. ### Math

Given sin30= 1/2 and cos30= (√3)/2 determine the following - csc30 I see the sin30 part can be used to find the answer, but what about the cos30 part?

asked by Anonymous on September 10, 2015
7. ### OPT MATHS

HOW TO PROVE(1+COS180/8)(1+COS3*180/8)(1+COS5*180/8)(1+COS7*180/8)=1/8

asked by BIMAL on October 15, 2015
8. ### pre-calculus

Graph the polar equation: 2=r cos(theta + 180) 2=r(costheta cos180+sintheta sin180) 2=r(1/2costheta +pi+ pi sintheta) 2=1/2rcostheta + pi rsintheta 2=1/2x+ pi y 4=x+ pi 0= x + pi-4 how do i graph?

asked by Mary on January 19, 2009