12th Std Formula
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COORDINATE GEOMETRY1 To change from Cartesian coordinates to polar coordinates, for X write r cos and for y write r sin . Write y and for tan x2 x1 y2
2
To change from polar coordinates to cartesian coordinates, for r2 write X2 + y2 ; for r cos write X, for r sin write .
.
3 Distance between two points (X1, Y1 ) and (X2 , Y2 ) is y1
4
5 Distance between (r1 , 1 ) and (r2 , 2 ) is 6 r
Distance of ( x1 , y1 ) from the origin is x
2 2 r 2 r1 r2 cos 2 1 1 2 Coordinates of the point which divides the line joining (X1 , Y1 ) and , ( m1 + m2
2 1
y
2 1
(X2, Y2 ) internally in the ratio m1 : m2 are :0)
7. Coordinates of the point which divides the line joining (X1 , Y1 ) and (X2 ,Y2 ) externally in the ratio m1 : m2 are :, (m1 m2 0)
8. Coordinates of the midpoint (point which bisects) of the seg. Joining (X1, y1) and (X2 y2 ) are :
, 9. (a) Centriod is the point of intersection of the medians of triangle. (b) Incentre is the point of intersection of the bisectors of the angles of the triangle. (c) Circumcentre is the point of intersection of the right (perpendicular) bisectors of the sides of a triangle. (d) Orthocentre is the point of intersection of the altitudes (perpendicular drawn from the vertex on the opposite sides) of a triangle. 10.Coordinates of the centriod of the triangle whose vertices are (x1 , y1 ) ; (x2 , y2 ) ; ( x3 , y3 ) are
11. Coordinates of the incentre of the triangle whose vertices are A (x1 ,y1) ; B (x2 ,y2 , ) ; C (x3 ,y3 ) and 1 (BC ) c. are . a, 1 (CA) b, 1 (AB)
12 Slope of line joining two points (x1 ,y1) and (x2 ,y2 )is m 13. Slope of a line is the tangent ratio of the angle which the line makes with the positive direction of the xaxis. i.e. m tan
14. Slope of the perpendicular to xaxis (parallel to y axis) does not exist, and the slope of line parallel to xaxis is zero.
15.
Intercepts: If a line cuts the xaxis at A and yaxis at B then OA is Called intercept on xaxis and denoted by a and OB is called intercept on yaxis and denoted by b.
16. X a is equation of line parallel to yaxis and passing through (a, b) and y b is the equation of the line parallel to xaxis and passing
through (a, b). 17. X 0 is the equation of yaxis and y 18. Y 0 is the equation of xaxis.
mx is the equation of the line through the origin and whose slope
is m. 19. Y mx +c is the equation of line in slope intercept form. 20. + 1 is the equation of line in the Double intercepts form,
where a is xintercept and b is yintercept. 21. X cos a + y sin a is the length of perpendicular from the origin on the line and is the direction of xaxis. 22. Y Y1 m (x x1 ) is the slope point form of line which passes through p is the equation of line in normal form, where p
angle which the perpendicular (normal) makes with the positive
(x1 , y1)and whose slope is m. 23. Two points form:  yy1 (x x1) is the equation of line which
Passes through the points (x1, y1) and (x2, y2). 24. Parametric form :r is the equation of line which
passes through the point (x1 y1 )makes an angle with the axis and r is the distance of any point (x, y) from ( x1, y1 ). 25. Every first degree equation in x and y always represents a straight line ax + by + c (a) Slope 0 is the general equation of line whose. 
(b) X  intercept
(c) Y intercept

26. Length of the perpendicular from (x1, y1 ) on the line ax + by + c 0 is
27. To find the coordinates of point of intersection of two curves or two lines, solve their equation simultaneously.
28. The equation of any line through the point of intersection of two given lines is (L.H.S. of one line) +K (L.H.S. of 2nd line) (Right Hand Side of both lines being zero) 0
TRIGONOMETRY29. SIN2 30. tan Cosec 31. 1 + tan2 Sec2  tan2 Cos2 + Cos2 1 Sin2 ; cot ; cot sec2 1 cosec2 ; cot2  cot2 Y 1 cosec2 1; ; tan2 sec2 1; ; sec ; 1; Sin2 1  Cos2 ,
32. 1 + cot2 Cosec2 33.
Only sine and cosec are positives O X1 III Only tan and cot are positives
all trigonometric ratios are positives X IV only cos and sec are positives
Y1
34.
angle 300 ratio 00 O 6 1 2 450 600 3 900 1200 2 3
Sin
0
1350 1500 3 4
1800
1
0
Cos
1
Tan
0
1
3
1 2
0

1 1
3
1
3.
0
35. Sin (36. sin (90
) =  Sin
;
cos ( ) = cos
;
tan ( ) =  tan
)
cos sin cot tan cosec
sin (90 + cos (90 +
)
cos sin cot tan cosec
sin (180 cos (180
)
sin cos tan cot sec cosec
sec (90 )
cot (90 )
tan (90 )
cos (90 )
tan (90 + ) cot (90+ )
tan ( 180 ) cot (180 ) sec (180 )
sec (90 + )
cosec (90 ) sec
cosec (90 + ) = sec
cosec (180 )
37. Sin (A + B) = SinA CosB + CosA SinB Sin (A  B) = CosA SinB  SinA CosB Cos (A + B) = CosA CosB  SinA CosB Cos (A B) = CosA CosB + SinA SinB tan (A + B) = tan (A  B) = 38. tan tan 39. A
A cos sin cos sin
SinC + SinD = 2 sin SinC  SinD = 2 cos CosC + CosD = 2 cos CosC  CosD = 2 sin
40.
2 sin A cos B = sin (A + B) + sin (AB) 2 cos A sin B = sin (A + B)  sin (AB) 2 cos A COS B 2 sin A sin B cos ( A +B) + cos (AB) cos (AB)  cos (A + B)
41. Cos (A +B). cos ( A  B ) = cos2A  sin2B Sin (A +B). sin (A B) = sin2A  sin2B
42. Sin 2 = 2 sin cos = 43. Cos2 =cos2  sin2 = 2cos2 1 = 1 2 sin2 = ;
44. 1 + cos 2 = 2 cos2 ; 1 cos 2 = 2 sin2 45. tan 2 = 46. sin 3 cos 3 tan 3 = 3 sin = 4 cos 3 = ;
 4 sin 3 ;  3 cos ;
47.
=
=
48. Cos A = Cos C
; ;
Cos B
;
49. a = b cos C + c cos B; b = c cos A + a cos C ;
c = a cos B + b cos A
50. Area of triangle =
bc sin A = ca sin B = ab sin c
51. 1
sin A = (cos A/2 tan A = tan
sin A/2)2 /2
52. sec A
53. Cosec A  cot A = tan A/2 54. Cosec A + cot A = cot A/2
PAIR OF LINES1. A homogeneous equation is that equation in which sum of the powers of x and y is the same in each term. 2. If m1 and m2 be the slopes of the lines represented by ax2 + 2hxy + by2 = 0, then m1 + m2 + and m1 +m2 = = =
3. If be the acute angle between the lines represented by ax2 + 2hxy + by2 = 0, then tan =
These lines will be co incident (parallel) if h2 = ab and perpendicular if a +b = 0. 4. The condition that the general equation of the second degree viz ax2 + 2hxy + by2 +2gx +2fy + c = 0 may represent a pair of straight line is abc + 2fgh af2 bg2  ch2 = 0
i.e.
= 0.
5. Ax2 + 2hxy + by2 = 0 and ax2 + 2hxy + by2 +2gx +2fy + c = 0 are pairs of parallel lines. 6. The point of intersection of lines ax2 + 2hxy + by2 + 2gx + 2fy + c = 0 is obtained by solving the equation ax + hy + g = 0 and hx + by + f = 0. 7. Joint equation of two lines can be obtained by multiplying the two equations of lines and equating to zero. (UV =0, where u = 0, v = 0). 8. If the origin is changed to (h,k) and the axis remain parallel to the original axis then for x and y put x + h and y + k respectively.
CIRCLE1. X2 + y2 = a2 is the equation of circle whose centre is (0, 0) and radius is a. 2. (x h) 2 + (y  k) 2 = a2 is the equation of a circle whose centre is (h, k) and radius is a.
centre is (g ,f) and radius is g f c. 4. Diameter form:  (x x1) (x x2) + (y y1) (y y2) = 0 is the equation of a circle whose (x1, y1) and (x2 , y2) are ends of a diameter. 5. Condition for an equation to represent a circle are : (a) Equation of the circle is of the second degree in x and y. 3. (b) The coefficient of x2 and y2 must be equal.
X2 + y2 + 2gx + 2fy + c = 0 is a general equation of circle, its
(c) There is no xy term in the equation (coefficient of xy must be zero). 1. To find the equation of the tangent at (x1 , y1 ) on any curve rule is: In the given equation of the curve for x2 put xx1 ; for y2put yy1 ; for 2x put x+ x1 and for 2y put y +y1 2. For the equation of tangent from a point outside the circle or given slope or parallel to a given line or perpendicular to a given line use y = mx + c or y y1 = m (x x1). 3. For the circle x2 + y2 = a2 (a) Equation of tangent at (x1, y1) is xx1 + yy1 = a2 (b) Equation of tangent at (a cos , a sin = a. (C) Tangent in terms of slope m is ) is x cos + y sin
Y = mx a 1 4. For the circle x2 + y2 + 2gx + 2fy + c = 0 (a) Equation of tangent at (x1, y1 ) is Xx1 + yy1 + g (x + x1) + f ( y + y1 ) + c = 0 (b) Length of tangent from (x1, y1) is 2 1 2 1 2 1 2 1
10. For the point P (x, y) , x is abscissa of P and y is ordinate of P.
PARABOLA1. Distance of any point P on the parabola from the focus S is always equal to perpendicular distance of P from the directrix i.e. SP = PM. 2. Parametric equation of parabola y2 = 4ax is x = at2, y = 2at. Coordinates of any point (t) is (at2 , 2at) 3. Different types of standard parabola Parabola Focus Directrix
Latus rectum
Axis of Parabola (axis of symmetry)
Y2 = 4ax Y2 =  4ax X2 = 4by X2 =  4by
(a, 0) (a, 0) (0, b) (0, b)
X = a X = a Y = b Y = b
4a 4a 4b 4b
Y = 0 Y = 0 X =0 X =0
4. For the parabola y2 = 4ax (a) Equation of tangent at (x1, y1) is Yy1 = 2a (x + x1).
2 (b) Parametric equation of tangent at (at , 2at1) is 1 yt1 = x + at21 (c) Tangent in term of slope m is y = mx + contact is (a/m2, 2a/m) (d) If P (t1) and Q (t2) are the ends of a focal chord then t2 t1 = 1 (e) Focal distance of a point P (x1