## Jaweria 2 years ago Can anyone please help me with this question? Find Y prime: Y=cos^-1(2x+5).

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1. Jaweria

This is the equation: $Y=\cos^{-1} (2x+5)$

2. Jaweria

This is a new math to me and the homework is due tomorrow I m stuck with these problems!!

3. Jaweria

I got an answer but it looks weird

4. mathsmind

5. rnick

what did you get? And next time, i recommend you go to the Calculus section, not the math.

6. Jaweria

its $2x /\sqrt{1-4x+25}$

7. mathsmind

(2x+5)=cosy

8. mathsmind

-dy/dxsiny=2

9. mathsmind

dy/dx=-2/siny

10. Jaweria

oh so there wont be 2x anymore

11. mathsmind

yup correct ur error, u'll get used to the method by practicing

12. Jaweria

hmm ok

13. mathsmind

it's ok to make error because from them u learn, but don't get turned off because of errors and ur close in ur answer

14. mathsmind

ur not that far

15. Jaweria

ok i know that numerator will be 2 but under radical is that also wrong?

16. Jaweria

i m sorry i know i am asking too many stupid questions

17. mathsmind

no ask any qs u like there isn't a stupid question in maths

18. Jaweria

okyyy :)

19. mathsmind

ok let me surprise u

20. Jaweria

alright i m waiting for my surprise

21. mathsmind

|dw:1360124524210:dw|

22. mathsmind

can u solve the rest and tell me where did u make the mistake

23. Jaweria

alright i am

24. mathsmind

now ur final answer should be

25. mathsmind

$\frac{ dy }{ dx }=\frac{ 1 }{ \sqrt{-x^2-5x-6} }$

26. mathsmind

is the script clear because i am writing using a normal mouse

27. Jaweria

yeah thats fine

28. Jaweria

I m actually multiplying 2x by the power of 2 so its 4x and multipylinh 5 by the power of 2 so its giving me 25

29. mathsmind

by the way give me the other 2 equations so u try and i try to solve the problem

30. mathsmind

and this way we can save time

31. Jaweria

oh ok

32. Jaweria

but before I do that one more question just one last time can you please show me that how you got that answer on the numerator is 1 and denominator is different too.

33. Jaweria

just last time then after that I ll do my other 3

34. mathsmind

sure

35. Jaweria

thanks

36. mathsmind

|dw:1360125108009:dw|

37. mathsmind

|dw:1360125325494:dw|

38. mathsmind

can u see the answer now

39. mathsmind

r u there?

40. Jaweria

yeah sorry i was focusing deeply to that answer

41. Jaweria

sorry one more question

42. Jaweria

how you got 5 under that radical?

43. mathsmind

44. Jaweria

bcoz once you took 4 out then 10 doesnt come into table of 4

45. mathsmind

sorry its 20 not 10

46. Jaweria

but how we are getting 20?

47. mathsmind

because (2x+5)^2= 4x^2 + 20x +25

48. mathsmind

and 25-1=24

49. mathsmind

4x^2+20x+24, 4(x^2+5x+6)

50. Jaweria

oh GOD whats wrong with me seriously my brain really isnt working I m still stuck with this 20

51. Jaweria

I m trying to figure out that how we got 20 it looks like I forgot basic math too

52. mathsmind

|dw:1360126122644:dw|

53. mathsmind

u haven't ur just feeling tired i know u r clever

54. Jaweria

yeah no doubt I m tired I had a classes today from 8:45am to 7:05 pm

55. Jaweria

thanks though

56. mathsmind

what's ur major?

57. Jaweria

Information Science

58. mathsmind

ok good

59. Jaweria

ok but once you will cancel that 2 out from denominator of 4, arent you not suppose to get 2 in denominator?

60. mathsmind

not because its root4=2

61. mathsmind

remember we took the 4 out of the root

62. Jaweria

$1/2\sqrt{-x ^2{}}-5x-6$

63. mathsmind

|dw:1360126668198:dw|

64. Jaweria

yeah we did take the 4 out from the root but we are also canceling that 2 with 4 right?

65. mathsmind

so u can see when we took the 16 out of the root it became 4

66. mathsmind

no cancelling the 2 with root4

67. Jaweria

oh ok

68. mathsmind

again let me show u

69. mathsmind

|dw:1360126822923:dw|

70. Jaweria

alright sir I got it now thank you so much for your patience and big help :)

71. Jaweria

I really appreciated

72. mathsmind

ur welcome

73. mathsmind

by the way how does this smart score work

74. mathsmind

and kindly send me the other 3 questions

75. Jaweria

oh I never worked on that smart score thing sorry

76. Jaweria

oh ok I will share with you these questions

77. Jaweria

$Y=\arctan(\sqrt{cscx})$

78. mathsmind

hehehe wow that is a long solution but not bad, with our method we can solve almost any question

79. Jaweria

$Y=\sec ^{-1}(e ^{x2})$

80. Jaweria

yeah

81. Jaweria

and one last question of this homework is: $Y=arc \cot(\sec 5x ^{3})$

82. mathsmind

that last function e^x^2 is how ur iphone works by the way

83. mathsmind

84. Jaweria

lolz I dont have an iphone I carry that ordinary phones

85. mathsmind

now u really have some chain rules here u have to be accurate

86. Jaweria

hmm ok

87. Jaweria

seriously i m giving up now I cant do this anymore ;(

88. Jaweria

I m just so tired and again I have classes tomorrow frm 8:45 am and its all due tomorrow its already 12:22 am here

89. mathsmind

by the way u can use the tables

90. mathsmind

it would be faster

91. mathsmind

ok all the best

92. mathsmind

i will solve them for u

93. Jaweria

hmm I feel bad though but if you can I really appreciate it

94. mathsmind

its ok see u tomorrow

95. Jaweria

alright thank u soo much though for your help. :) take care bye.