In prove of cos(x+y)=cosx.cosy-sinx.siny
it is given that the line which makes angle x(degrees) has the coordinates "cosx,sinx"(in 2nd quadrant).I understand that in circle of radius 1 which makes angle x in first quadrant will have cordinates cosx,sinx on the circle.and i think it should be -cosx,sinx for 2nd quadrant but in ncert book pg no.64 In prove of cos(x+y)=cosx.cosy-sinx.siny fig 3.14 it is given that in 2nd quadrant too the value is cosx,sinx.can you explain how?
also can you explain sin 90+x=-cosx by diagram or prove geometrically?
Asked by Kamlesh Sahu | 7th May, 2014, 06:41: AM
The proof in the NCERT book is correct . These points are basically parametric coordinates of a circle, whose values depend upon the arguments( x & y) of cosine and sine functions.
For second question
Answered by Avinash Soni | 7th May, 2014, 03:49: PM
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