1) Find dtdy for y=costt2sint
Step 1: Rewrite the expression for y using trigonometric identities.
We know that costsint=tant.
So, we can write y as:
y=t2tant
Step 2: Apply the product rule for differentiation.
The product rule states that if y=u⋅v, then dtdy=u′v+uv′.
Let u=t2 and v=tant.
Then, u′=dtd(t2)=2t.
And v′=dtd(tant)=sec2t.
Step 3: Substitute u,v,u′,v′ into the product rule formula.
dtdy=(2t)(tant)+(t2)(sec2t)
dtdy=2ttant+t2sec2t
The derivative is 2ttant+t2sec2t.
2) If y=costt2sint, show that t2dt2d2y+4tdtdy−(t2+6)y=0.
Step 1: Use the result from for dtdy and the expression for y.
We have y=t2tant and dtdy=2ttant+t2sec2t.
Step 2: Find the second derivative, dt2d2y.
We need to differentiate dtdy with respect to t:
dt2d2y=dtd(2ttant+t2sec2t)
Differentiate 2ttant using the product rule:
dtd(2ttant)=(2)(tant)+(2t)(sec2t)=2tant+2tsec2t.
Differentiate t2sec2t using the product rule and chain rule:
dtd(t2sec2t)=(2t)(sec2t)+(t2)(2sect⋅secttant)=2tsec2t+2t2sec2ttant.
Combine these two results for dt2d2y:
dt2d2y=(2tant+2tsec2t)+(2tsec2t+2t2sec2ttant)
dt2d2y=2tant+4tsec2t+2t2sec2ttant
Step 3: Substitute y, dtdy, and dt2d2y into the left-hand side of the given equation.
The left-hand side (LHS) is t2dt2d2y+4tdtdy−(t2+6)y.
Substitute the expressions:
LHS=t2(2tant+4tsec2t+2t2sec2ttant)
+4t(2ttant+t2sec2t)
−(t2+6)(t2tant)
Step 4: Expand and simplify the expression.
Expand each term:
t2dt2d2y=2t2tant+4t3sec2t+2t4sec2ttant
4tdtdy=8t2tant+4t3sec2t
−(t2+6)y=−t4tant−6t2tant
Now, sum these expanded terms:
LHS=(2t2tant+4t3sec2t+2t4sec2ttant)
+(8t2tant+4t3sec2t)
+(−t4tant−6t2tant)
Group terms by tant:
(2t2+8t2−6t2−t4)tant=(4t2−t4)tant
Group terms by sec2t:
(4t3+4t3)sec2t=8t3sec2t
Group terms by sec2ttant:
2t4sec2ttant
Combining these, the LHS simplifies to:
LHS=(4t2−t4)tant+8t3sec2t+2t4sec2ttant
This expression does not simplify to 0. It is possible there is a typo in the question.
3) If y=tn show that dtdy=ntn−1.
Step 1: Apply the power rule for differentiation.
The power rule states that if y=tn, then dtdy=ntn−1.
Given y=tn.
dtdy=ntn−1
This is a direct application of the power rule.
The derivative is ntn−1.
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